bluuebunny/crossref_metadata_2025 huggingface dataset:
A first-principles study on the electronic property and magnetic anisotropy of ferromagnetic CrOF and CrOCl monolayers
Authors: Xu Chunyan , Zhang Jing , Guo Zexuan , Zhang Siqi , Yuan Xiaoxi , Wang Lingrui
Published: February 2021

Two-dimensional ferromagnetic materials with large perpendicular magnetic anisotropy (PMA) hold great potential in realizing low critical switching current, high thermal stability and high density nonvolatile storage in magnetic random-access memories. Our first-principles calculations reveal that CrOF and CrOCl monolayers (MLs) are two-dimensional (2D) ferromagnetic semiconductors with out-of-plane magnetic easy axis, and PMAs of CrOF and CrOCl MLs are mainly contributed by Cr atoms. The magnetic anisotropy of CrOF and CrOCl MLs can be controlled and enhanced by applying biaxial strain. Tensile strain can further enhance PMAs of CrOF and CrOCl MLs by 82.9% and 161.0% higher than those of unstrained systems, respectively. In addition, appropriate compressive strain can switch the magnetic easy axis of CrOF and CrOCl MLs from out-of-plane direction to in-plane direction. The semiconductor natures of CrOF and CrOCl MLs robust against biaxial strain, the band gaps of these systems under biaxial strain are in the range of 1.26 eV to 2.40 eV. By applying biaxial strain, the Curie temperatures of CrOF and CrOCl MLs increase up to 282 K and 163 K, respectively. These tunable properties suggest that CrOF and CrOCl MLs have great application potentials for magnetic data storage.
Temperature-dependent change of the electronic structure in the Kondo lattice system YbRh2Si2
Authors: Agustsson S Y , Chernov S V , Medjanik K , Babenkov S , Fedchenko O , Vasilyev D , Schlueter C , Gloskovskii A , Matveyev Yu , Kliemt K , Krellner C , Demsar J , Schönhense G , Elmers H-J
Published: February 2021

The heavy-fermion behavior in intermetallic compounds manifests itself in a quenching of local magnetic moments by developing Kondo spin-singlet many-body states combined with a drastic increase of the effective mass of conduction electrons, which occurs below the lattice Kondo temperature T
K. This behavior is caused by interactions between the strongly localized 4f electrons and itinerant electrons. A controversially discussed question in this context is how the localized electronic states contribute to the Fermi surface upon changing the temperature. One expects that hybridization between the local moments and the itinerant electrons leads to a transition from a small Fermi surface in a non-coherent regime at high temperatures to a large Fermi surface once the coherent Kondo lattice regime is realized below T
K. We demonstrate, using hard x-ray angle-resolved photoemission spectroscopy that the electronic structure of the prototypical heavy fermion compound YbRh2Si2 changes with temperature between 100 and 200 K, i.e. far above the Kondo temperature, T
K = 25 K, of this system. Our results suggest a transition from a small to a large Fermi surface with decreasing temperature. This result is inconsistent with the prediction of the dynamical mean-field periodic Anderson model and supports the idea of an independent energy scale governing the change of band dispersion.
High-field phase diagram of Ni3V2O8 studied by specific heat and magnetocaloric effect measurements
Authors: Dong C , Kohama Y , He Z Z , Han X T , Sato K , Matsuo A , Kindo K , Yang M , Wang J F
Published: February 2021

The H–T phase diagram of Ni3V2O8 is very rich and remains puzzling in a high magnetic field range. Through the state-of-the-art specific heat measurement in pulsed high field to 35 T and magnetocaloric effect measurement up to 45 T, we successfully construct the high-field phase diagram of Ni3V2O8 for fields applied along the b axis. The phase boundaries are corrected for previous results by magnetization and magneto-optical measurements. The resulting phase diagram shows that the high temperature incommensurate (HTI) phase develops well to high fields and low temperatures. In addition to the early reported C′, C, low temperature incommensurate (LTI) and HTI phases, we explore a new magnetic ordered phase called HF1 in fields of 10–30 T. A multicritical point is also observed at 6 K and 8 T. Furthermore, the specific heat data reveal enhancements of the anomalies at ∼4 K, probably associated with a strong spin–lattice coupling in this frustrated multiferroic material.
Temperature evolution of 3d- and 4f-electron magnetic ordering in the ferrimagnetic Mn self-doped perovskite (Yb0.667Mn0.333)MnO3
Authors: Dönni Andreas , Pomjakushin Vladimir Y , Zhang Lei , Yamaura Kazunari , Belik Alexei A
Published: February 2021

A high-pressure synthesis method was employed to prepare Mn-self-doped perovskites (R
0.667Mn0.333)MnO3 (R = Yb, Lu) at about 6 GPa and 1670 K. Crystal and magnetic structures of (Yb0.667Mn0.333)MnO3 have been studied by combining neutron powder diffraction, magnetic susceptibility and specific heat measurements. Within the orthorhombic space group Pnma, magnetic cations are located on site 4c (A site, occupied by two thirds of Yb3+ and one third of Mn2+) and on site 4b (B site, occupied by two thirds of Mn3+ and one third of Mn4+). The degree of structural distortion of the MnO6 octahedra follows the general trend of (R1−x
Mn
x
)MnO3 compounds which shows a decrease with increasing amount of Jahn–Teller inactive Mn4+ cations. Mn–Mn interactions produce a collinear ferrimagnetic structure (T
C,Mn = 106 K) with ferromagnetically ordered Mn moments at the B site being coupled antiferromagnetically with ordered Mn moments at the A site. Mn–Yb interactions induce a small but non-zero ferromagnetic Yb3+ moment which can explain a small decrease of the magnetic susceptibility at low temperature. Yb–Yb interactions create an antiferromagnetic structure at T
N,Yb ≈ 40 K. Ordered moments of the ferrimagnetic and antiferromagnetic structures are oriented perpendicular to each other within the ac-plane and Yb3+ moments contribute to both structures. The appearance of ordered Yb3+ moments induced by Mn–Yb interactions in perovskite (Yb0.667Mn0.333)MnO3 is a result of the Mn self-doping on the A site and has not been observed in the orthorhombic perovskite modification (space group Pnma) of the undoped parent compound YbMnO3, but interestingly, it also appears in the hexagonal non-perovskite modification (space group P63
cm) of YbMnO3.
Improved clearance verification
Authors: Meck Robert A , Jiselmark Jonatan
Published: February 2021

This paper describes clearance as the sum of fractions (SOF) inequality with acceptable probability. We include scenario modelling uncertainties in SOF calculations. An illustrative contrast of results with and without the modelling uncertainties shows the differences in the probabilities that the standards were met. We present two methods for calculations, the analytical approach, GUM, and the Monte Carlo (MC) method. We prefer the MC. Inclusion of the scenario uncertainties can provide improved assurance that people are adequately protected. An example that used data from a Swedish reactor is included.
Uncertainty evaluation in atomic force microscopy measurement of nanoparticles based on statistical mixed model in a Bayesian framework
Authors: Pétry J , Boeck B De , Sebaïhi N , Coenegrachts M , Caebergs T , Dobre M
Published: February 2021

A major bottleneck in nanoparticle sizing is the lack of data comparability between techniques and between laboratories. However, this can be overcome by making the measurements traceable to the SI together with realistic uncertainty evaluation. In the present work, a novel approach is proposed to perform measurement uncertainty evaluation in a Bayesian framework by statistically modeling appropriately selected measurement data when no comprehensive physical model is available. The method is applied to the dimensional measurement of nanoparticles by atomic force microscopy (AFM) measurement and the calibration is performed by a multiple points calibration curve. Nevertheless, the proposed method can be applied to other microscopy techniques. The experimental data used to construct the statistical model are collected so that the influence of relevant measurement parameters can be assessed. An optimized experiment is designed under the intermediate precision conditions in order to limit the number of measurements to perform. Among the different influencing parameters, it is found that the AFM operator and image analyst do not significantly affect the measurement variability while the tip tapping force, the probe nature and the tip scan speed do. The particular case of gold nanoparticle of nominal diameter 30 nm is treated as an example of the method.
Modifying the theoretical model of the target indirect measurement method for measuring the thrust of electric propulsion
Authors: Weng Huiyan , Cai Guobiao , Liu Lihui , Zheng Hongru , Zhang Mingxing , Zhang Baiyi , He Bijiao
Published: February 2021

Electric propulsion systems, such as ion thrusters and Hall thrusters, are widely utilized in aerospace. The target indirect measurement method (TIMM) is a simple and robust way to measure its thrust. In general, one can obtain the thrust by scaling up the force exerted on the target surface immersed in the plume flow. However, the charge exchange (CEX) allows ions to become neutral particles, increasing the scaling coefficient. Meanwhile, the sputtered atoms and reflected incident particles exert force on the target surface and enlarge the measured thrust. In this study, the effects of the CEX, the sputtering, and the reflection on the TIMM are mathematically quantified, and then a modified model of the TIMM is proposed. Besides, the thrusts of the LIPS-200 and LIPS-300 ion thrusters were separately measured using the TIMM with the modified model, and the measured thrusts are in good agreement with the rated thrusts. Under the test conditions, the results of the LIPS-300 ion thruster show that the fast neutral atoms produced by the CEX account for more than 20% of all fast particles impacting on the target, and the force caused by the sputtered atoms is about 3.4% of the total force exerted on the target. We discuss how test conditions affect the CEX, sputtering, and reflection, thereby influencing the TIMM. The modified model was also validated through the simulation results, by showing that the measured thrust cannot be influenced by the test conditions.
A variational fast Fourier transform method for phase-transforming materials
Authors: Cruzado A , Segurado J , Hartl D J , Benzerga A A
Published: February 2021

A fast Fourier transform (FFT) based method is developed to model the pseudo-elastic behavior and shape-memory effect in phase transforming materials. An infinitesimal strain based variational FFT formulation is adapted and enhanced to enable the solution of nonlinear, stress-controlled and thermo-mechanical problems. The capabilities of the method are illustrated by implementing a computational homogenization approach to modeling the thermo-mechanical response of shape memory alloys with heterogeneities. The accuracy and performance of the method is evaluated by comparison with finite element (FE) solutions for single- and multi-particle cells subjected to various loading schemes. For the class of nonlinear problems of interest, the proposed method is shown to be an order of magnitude faster than the FE method for a given resolution, and possibly for the same accuracy.
Highly sensitive nanoparticle sensing based on a hybrid cavity in a freely suspended microfiber
Authors: Cheng Qi , Wang Shutao , Lv Jiangtao , Wang Junzhu , Liu Na
Published: February 2021

We report a hybrid cavity structure based on a suspended microfiber with a diameter of 1.7 μm applied to nanoparticle sensing in water. The proposed hybrid cavity is composed of two symmetrical reflectors with a slotted Au layer in the middle. After being characterized by the finite-difference time-domain method, the obtained strong reflection and sufficiently wide band gap provide the potential to realize an ultrasmall mode volume, which can improve sensitivity and lower loss. In addition, an ultrahigh Q/V ratio of 8.2 × 106 (λ/n)−3 and high resonance transmittance of T = 0.53 can be obtained through optimization analysis. After analyzing the trapping force and resonance shift caused by the change in local electric field, it is proven that our proposed cavity exhibits a high sensitivity and offers a convenient and stable method for particle sensing in water.
Magnetically responsive polymer nanopillars with nickel cap
Authors: Luo Zhiren , Zhang Xu A , Chang Chih-Hao
Published: February 2021

Embedding magnetic particles within polymer matrix is a common and facile method to fabricate magnetically responsive micro-/nanoscale pillars. However, the balance between mechanical compliance and magnetic susceptibility cannot be decoupled and the particles are limited by the pillar feature size, which can limit the actuation performance. Here we demonstrate a new type of magnetically responsive nanostructure consisting of a polydimethylsiloxane (PDMS) nanopillar array with deposited nickel caps, that has successfully achieved such decoupling with multiple cap-geometry designs for a better actuation control. The actuation result of nanopillars with 540 nm period and 1.3 μm height has been analyzed using image processing, leading to a maximum displacement of 180 nm with a ratio of 13.9% with respect to the pillar height. Magnetic and mechanical models based on magnetic force and torque have been developed and used to mitigate the weakening effect of the actuation by the residual magnetic layer. This structure demonstrates a feasible strategy for magnetic actuation at the sub-micrometer scale with freedom to design magnetic cap and polymeric pillar separately. This structure can also be utilized in multiple applications such as tunable optical elements, dynamic droplet manipulation, and responsive particle manipulation.
A minimally invasive electrostatic particle extractor for nanodusty plasmas and its application for the verification of in situ Mie polarimetry
Authors: Dworschak Maren , Asnaz Oguz Han , Greiner Franko
Published: February 2021

We present an electrostatic particle extractor system (EPEX) which extracts particles from a reactive, particle-growing plasma by using the electrostatic force. The system is able to extract eight samples during a single growth cycle without the need to interrupt the plasma process. Using video microscopy, imaging-Mie, and Mie polarimetry we demonstrate the minimal invasiveness of EPEX. The extraction voltage and its duration are optimized to tune the particle density on the sample wafer. Compared to other invasive extraction methods, EPEX is fast and reliable. Using atomic force microscopy the size of the particles can be determined from samples extracted from the nanodusty plasma during one growth cycle and can be compared to the results of simultaneously performed in situ Mie polarimetry for the first time. We show that the extraction process can be divided in three distinct phases and that its physics can be understood in the simple framework of the force balance for a single dust particle. Using this single particle model, we present a new method for determining the particle charge of dust particles in dense dusty plasmas. The determined particle charge of (−9.2 ± 2.8) elementary charges reveals a strong Havnes effect.
Continuum level-set model for anisotropic wet etching of patterned sapphire substrates
Authors: Toifl A , Rodrigues F , Aguinsky L F , Hössinger A , Weinbub J
Published: February 2021

We present a continuum modeling approach to simulate anisotropic wet etching of single-crystal sapphire employing mixtures of sulfuric acid and phosphoric acid. Wet etching of sapphire leads to the formation of crystal facets with high Miller–Bravais indices. The resulting complex three-dimensional topographies can be exploited to optimize the patterning of sapphire substrates which are employed for gallium nitride based light-emitting diodes. Due to the strong impact of the three-dimensional sapphire topography on the light extraction efficiency of the final device, precise control over the wet etching process, in particular etchant mixture, etch time, and temperature, is highly important. We present our model in the context of process technology computer-aided design, where we use the level-set method to track the evolution of the three-dimensional etch profile over time. In order to describe the intricate anisotropy of wet etched sapphire, we propose a flexible interpolation method for the etch rate distribution, which incorporates experimentally characterized crystal facets and deduces local extrema in the distribution based on local convexity/concavity considerations. The developed model has been calibrated and evaluated based on scanning electron microscopy and atomic force microscopy characterizations from the literature. Our model enables accurate sapphire etching simulations, where the emerging and disappearing crystal facets show a good agreement with experimental observations for several etchant mixtures and temperatures.
Influence of Al content on ZnO/Al bilayer-structure ultraviolet photodetector
Authors: Si Jiawei , Song Wenqing , Wang Liancheng , Zhu Wenhui , Zhang Lei
Published: February 2021

As a potential optoelectronic material, the use of ZnO in ultraviolet (UV) photodetectors is attracting significant attention. In this study, aluminum (Al) nanoparticles of different content and ZnO films are sequentially sputtered to form ZnO/Al bilayer UV photodetectors. The responsivity of the ZnO/Al bilayer photodetector, with a maximum of 380.9 A W−1 at 320 nm and 5 V bias, is higher than that of the single-layer ZnO photodetector. The enhanced responsivity of the ZnO/Al bilayer UV photodetectors can be attributed to the local surface plasmon resonance effect and the introduction of oxygen vacancies. Meanwhile, the different size and distribution density of Al nanoparticles determines the different enhanced mechanisms. Our work provides a promising route to design and fabricate a high-performance photodetector.
Damage detection in large composite stiffened panels based on a novel SHM building block philosophy
Authors: Yue Nan , Khodaei Zahra Sharif , Aliabadi M H
Published: February 2021

This paper proposes a structural health monitoring (SHM) building block (BB) approach for guided wave based structural health monitoring (GWSHM) of large composite stiffened panel subjected to varying temperature conditions. The proposed approach follows a similar philosophy to industrial substantiation of composite structures through BB by conducting SHM analysis and associated tests at different levels of structural complexity, beginning with small coupon specimens and progressing through structural elements and details (mono-stringer) and finally sub-components (large stiffened composited panel). Each level builds on the knowledge gained at previous, less complex levels. The detection of multiple barely visible impact damage (BVID) in the large panels is achieved by outlier analysis using a reference pristine database gathered from simple coupons and mono-stringer panels under a wide range of temperature variation. This approach enables the data utilisation from lower-level structure in the proposed BB test scheme to higher-level structures and hence reduce the number of tests required for large and complex structures. The detected damage is then localised by a proposed two-step multi-damage localisation method, which first confirms the presence of the damage and narrows down the damaged section then provides an enhanced damage imaging for precise location estimation. Damage detection with a true positive rate of 0.909 and a false positive rate of 0.111 as well as accurate multiple damage localisation are achieved in the flat fuselage panels for a temperature range of 25 °C–50 °C.
Multi-photon resonances in Josephson junction-cavity circuits
Authors: Lang Ben , Armour Andrew D
Published: February 2021

We explore the dissipative dynamics of nonlinearly driven oscillator systems tuned to resonances where multiple excitations are generated. Such systems are readily realised in circuit QED systems combining Josephson junctions with a microwave cavity and a drive achieved either through flux or voltage bias. For resonances involving three or more photons the system undergoes a sequence of two closely spaced dynamical transitions (the first one discontinuous and the second continuous) as the driving is increased leading to steady states that form complex periodic structures in phase space. In the vicinity of the transitions the system displays interesting bistable behaviour: we find that coherent effects can lead to surprising oscillations in the weight of the different dynamical states in the steady state of the system with increasing drive. We show that the dynamics is well-described by a simple effective rate model with transitions between states localised at different points in the phase space crystal. The oscillations in the weights of the dynamical states is reflected in corresponding oscillations in a time-scale that describes transitions between the states.
Theoretical investigations on HgTe chalcogenide materials under high pressure
Authors: Duz I , Kart H H , Ozdemir Kart S , Kuzucu V
Published: February 2021

First principle computations based on Density Functional Theory are made to investigate structural, mechanical, electronic properties and phase transition behaviors of HgTe chalcogenide material. It is obtained that the phase transition sequence of HgTe material is Zincblende → Cinnabar → Rocksalt → Cmcm → CsCl at 2.35 GPa, 5.95 GPa, 14.29 GPa, 52.37 GPa, respectively. The negative

C

44

and

C

s

values of the CsCl structure under ambient conditions indicate that this structure is mechanically unstable against the applied deformations. The small values of the elastic constants of HgTe in the cinnabar structure reveal that this structure is less resistant to deformations. The low value of tetragonal shear constant Cs of the parent phase reflects the elastic instability leading to a pressure-induced phase transition. According to our isotropic mechanical results obtained from the Voigt-Reuss-Hill (VRH) approach, the ductility behavior improves in the rocksalt and Cmcm structures which are high-pressure phases. The zincblende and cinnabar structures show semimetal and semiconductor properties in the electronic band calculations, respectively, while rocksalt, Cmcm and CsCl structures are found to be of metallic character.
The upgraded ASDEX Upgrade contribution to the ITPA confinement database: description and analysis
Authors: Ryter F. , Angioni C. , Tardini G. , Birkenmeier G. , David P. , Dunne M. , Fischer R. , Pütterich T. , Schweinzer J. , Stober J. , ASDEX Upgrade Team The , EUROfusion MST1 Team The
Published: February 2021

The ITPA multi-machine confinement database has been recently extended, in particular to account for the effect of the metallic plasma facing components installed in the ASDEX Upgrade and JET tokamaks during the last decade. Confinement data from the ASDEX Upgrade tokamak have been contributed to the ITPA confinement database since 1994. The present version, which includes data from 1994 to 2017, is described and discussed in this article. The aim of this work is to document the database before it is made public and report on the main results on the confinement properties reflected in this database. Through the transition from carbon to metallic wall, the operation at low density originally accessible with the carbon wall, has been strongly limited by the occurrence of tungsten accumulation. However, at medium and high densities, the confinement properties with the carbon and metallic walls are rather similar. The database analysis yields in both cases a rather strong plasma current dependence and a clearly negative magnetic field dependence. The density dependence is negligible, while the well-known positive impact of triangularity appears very clearly. These dependences are partly at variance with the widely-used IPB98(y,2) confinement scaling, but in agreement with the analysis of the upgraded ITPA multi-machine and JET databases. The confinement degradation observed at high density with strong gas puffing can be clearly attributed to the density profile in the outer plasma region, as reported in previous studies.
Observation of TAE mode driven by off-axis ECRH induced barely trapped energetic electrons in EAST tokamak
Authors: Chu N. , Sun Y. , Shen B. , Hu Y.J. , Gu S. , Jia M. , Wang H.H. , Shi T.H. , Bao J. , Duan Y.M. , He K.Y. , Li E. , Liu H.Q. , Liu Y. , Lyu B. , Ma Q. , Qian J.P. , Ren J. , Ti A. , Wang H.L. , Wang S.X. , Wang X.J. , Wang Y.M. , Zang Q. , Zeng L. , Zhang J.Z. , Zhang T. , Zhang Y. , Zhao H.L. , Zhou R.J. , Zhou T.F.
Published: February 2021

A toroidal Alfvén eigenmode (TAE) is excited by electron cyclotron resonance heating (ECRH) induced barely trapped energetic electrons in experimental advanced superconducting tokamak . This TAE appears in the low density EAST discharges under pure off-axis ECRH heating. After analysing the ECRH power modulation induced local density and temperature oscillations, the location of this TAE mode and the power deposition of ECRH are determined. This edge localized TAE mode drifts in ion-diamagnetic direction may be driven by barely trapped energetic electrons considering the contribution of poloidal bounce effect in the general wave-particle resonance condition. The experimental observations also demonstrate that ECRH power modulation with fixed frequency could be used as an effective diagnostic tool to study the internal properties of MHD modes as well as particle and heat transports.
Numerical investigation of alpha particle confinement under the perturbation of neoclassical tearing modes and toroidal field ripple in CFETR
Authors: Hao Baolong , White Roscoe , Gao Xiang , Li Guoqiang , Chen Wei , Wang Xiaojing , Wu Bin , Wu Muquan , Zhu Xiang , Lin Xiaodong , Jie Yinxian , Zang Qing , Li Jiangang , Wan Yuanxi , Physics Team CFETR
Published: February 2021

The confinement of alpha particles in burning plasma is a key issue in fusion reactor design, including particle interaction with instabilities. This paper includes two topics: the effect of neoclassical tearing modes (NTMs) and toroidal field ripple on alpha particle loss, and the assessment of particle redistribution under an NTM with a reduced model. We consider Chinese fusion engineering test reactor parameters, the alpha particle distribution given by TRANSP/NUBEAM and the NTM perturbation function given by the initial value code TM1. We show that the synergistic effect of the NTM and ripple is negligible; the particle loss fraction does not change with increasing NTM amplitude. Only passing particles are affected by the mode particle resonance, producing profile flattening but no increased loss because only trapped particles are influenced by ripple. To study alpha particle profile flattening, the work adopts an innovative method of phase vector rotation to determine regions of good and broken Kolmogorov–Arnold–Moser surfaces and equilibrates the particle density according to local stochasticity.
Emergence of a finite-size-scaling function in the supervised learning of the Ising phase transition
Authors: Kim Dongkyu , Kim Dong-Hee
Published: February 2021

We investigate the connection between the supervised learning of the binary phase classification in the ferromagnetic Ising model and the standard finite-size-scaling theory of the second-order phase transition. Proposing a minimal one-free-parameter neural network model, we analytically formulate the supervised learning problem for the canonical ensemble being used as a training data set. We show that just one free parameter is capable enough to describe the data-driven emergence of the universal finite-size-scaling function in the network output that is observed in a large neural network, theoretically validating its critical point prediction for unseen test data from different underlying lattices yet in the same universality class of the Ising criticality. We also numerically demonstrate the interpretation with the proposed one-parameter model by providing an example of finding a critical point with the learning of the Landau mean-field free energy being applied to the real data set from the uncorrelated random scale-free graph with a large degree exponent.
Sensors track mobilization of ‘chemical cocktails’ in streams impacted by road salts in the Chesapeake Bay watershed
Authors: Galella Joseph G , Kaushal Sujay S , Wood Kelsey L , Reimer Jenna E , Mayer Paul M
Published: February 2021

Increasing trends in base cations, pH, and salinity of freshwaters have been documented in US streams over 50 years. These patterns, collectively known as freshwater salinization syndrome (FSS), are driven by multiple processes, including applications of road salt and human-accelerated weathering of impervious surfaces, reductions in acid rain, and other anthropogenic legacies of change. FSS mobilizes chemical cocktails of distinct elemental mixtures via ion exchange, and other biogeochemical processes. We analyzed impacts of FSS on streamwater chemistry across five urban watersheds in the Baltimore-Washington, USA metropolitan region. Through combined grab-sampling and high-frequency monitoring by USGS sensors, regression relationships were developed among specific conductance and major ion and trace metal concentrations. These linear relationships were statistically significant in most of the urban streams (e.g. R
2 = 0.62 and 0.43 for Mn and Cu, respectively), and showed that specific conductance could be used as a proxy to predict concentrations of major ions and trace metals. Major ions and trace metals analyzed via linear regression and principal component analysis showed co-mobilization (i.e. correlations among combinations of specific conductance (SC), Mn, Cu, Sr2+, and all base cations during certain times of year and hydrologic conditions). Co-mobilization of metals and base cations was strongest during peak snow events but could continue over 24 h after SC peaked, suggesting ongoing cation exchange in soils and stream sediments. Mn and Cu concentrations predicted from SC as a proxy indicated acceptable goodness of fit for predicted vs. observed values (Nash–Sutcliffe efficiency > 0.28). Metals concentrations remained elevated for days after SC decreased following snowstorms, suggesting lag times and continued mobilization after road salt use. High-frequency sensor monitoring and proxies associated with FSS may help better predict contaminant pulses and contaminant exceedances in response to salinization and impacts on aquatic life, infrastructure, and drinking water.
High-resolution forest carbon modelling for climate mitigation planning over the RGGI region, USA
Authors: Ma L , Hurtt G , Tang H , Lamb R , Campbell E , Dubayah R , Guy M , Huang W , Lister A , Lu J , O’Neil-Dunne J , Rudee A , Shen Q , Silva C
Published: February 2021

The inclusion of forest carbon in climate change mitigation planning requires the development of models able to project potential future carbon stocks—a step beyond traditional monitoring, reporting and verification frameworks. Here, we updated and expanded a high-resolution forest carbon modelling approach previously developed for the state of Maryland to 11 states in the Regional Greenhouse Gas Initiative (RGGI) domain, which includes Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, and Vermont. In this study, we employ an updated version of the Ecosystem Demography (ED) model, an improved lidar initialization strategy, and an expanded calibration/validation approach. High resolution (90 m) wall-to-wall maps of present aboveground carbon, aboveground carbon sequestration potential, aboveground carbon sequestration potential gap (CSPG), and time to reach sequestration potential were produced over the RGGI domain where airborne lidar data were available, including 100% of eight states, 62% of Maine, 12% of New Jersey, and 0.65% of New York. For the eight states with complete data, an area of 228 552 km2, the contemporary forest aboveground carbon stock is estimated to be 1134 Tg C, and the forest aboveground CSPG is estimated to be larger at >1770 Tg C. Importantly, these estimates of the potential for added aboveground carbon sequestration in forests are spatially resolved, are further partitioned between continued growth of existing trees and new afforested/reforested areas, and include time estimates for realization. They are also assessed for sensitivity to potential changes in vegetation productivity and disturbance rate in response to climate change. The results from this study are intended as input into regional, state, and local planning efforts that consider future climate mitigation in forests along with other land-use considerations.
New approach for predicting nitrification and its fraction of N2O emissions in global terrestrial ecosystems
Authors: Pan Baobao , Lam Shu Kee , Wang Enli , Mosier Arvin , Chen Deli
Published: February 2021

Nitrification is a major pathway of N2O production in aerobic soils. Measurements and model simulations of nitrification and associated N2O emission are challenging. Here we innovatively integrated data mining and machine learning to predict nitrification rate (

R

nit

) and the fraction of nitrification as N2O emissions (

f

N

2

O

Nit

). Using our global database on

R

nit

and

f

N

2

O

Nit

, we found that the machine-learning based stochastic gradient boosting (SGB) model outperformed three widely used process-based models in estimating

R

nit

and N2O emission from nitrification. We then applied the SGB technique for global prediction. The potential

R

nit

was driven by long-term mean annual temperature, soil C/N ratio and soil pH, whereas

f

N

2

O

Nit

by mean annual precipitation, soil clay content, soil pH, soil total N. The global

f

N

2

O

Nit

varied by over 200 times (0.006%–1.2%), which challenges the common practice of using a constant value in process-based models. This study provides insights into advancing process-based models for projecting N dynamics and greenhouse gas emissions using a machine learning approach.
Ground state of a cross-cavity quantum Rabi model
Authors: Shen Lituo , Yang Jingwen , Shi Zhicheng , Zhong Zhirong , Xu Canhua
Published: February 2021

We study a cross-cavity quantum Rabi model with ultrastrong coupling, and its analytical ground state is demonstrated to be approximately obtained by using the rotating-transformation method. Our method requires making three unitary transformations to the original Hamiltonian and ignoring the three-party cross interaction. In near-resonance and ultrastrong-coupling regimes, the ground-state fidelity is higher than 99% for a ±20% detuning range. We analytically demonstrate that the entanglement in ground state first quadratically increases with the qubit-oscillator coupling strength, then gets close to the maximum value 1. The oscillator’s nonclassical property in the ground state is well explained by analytically solving the Wigner function.
Affecting Factors for Implementing Performance-Based Maintenance Contracting: Perspective of Malaysian Road Contractors
Authors: Manogaran R , Rahman R A , Ismail A , Razelan I S M , Mandiartha P
Published: February 2021

Traditionally, road maintenance is conducted either using road authorities’ in-house resources or method-based contracting, where contractors do the work and are paid based on predefined volume and unit prices. Nowadays, Performance-based Maintenance Contracting (PBMC) is one of the most current approaches in road maintenance works. PBMC provides contractors with freedom in design, construction methods, materials, and innovation in performing the contract as long as the standard specified is fulfilled. While PBMC implementation is increasing around the world, it can be considered new in Malaysia. This research aims to investigate the viability and practicability of PBMC’s implementation for road maintenance in Malaysia. Specifically, the research’s objective is to identify factors that are affecting the adoption of PBMC for road maintenance works in Malaysia. To achieve that objective, interview data from industry practitioners that are involved in managing roads are analyzed. Factors affecting PBMC’s implementation for road maintenance in Malaysia can be categorized into two groups: PBMC (ex. awareness on PBMC) and Non-PBMC (ex. contractor’s integrity) related factors. The findings of this research would help policymakers, industry practitioners, and researchers improve the success of implementing PBMC in the facility management industry.
Online estimation of battery power state based on improved equivalent circuit model
Authors: Wang Yu
Published: February 2021

The state-of-power (SOP) of lithium-ion batteries is an important parameter for safety control and energy recovery of electric vehicles. In the battery management system (BMS), the Equivalent-Circuit Model (ECM) is commonly used to simulate battery dynamics. However, there is always a contradiction between the complexity and accuracy of the model. A simple model usually cannot reflect all the dynamic effects of the battery, which may bring error identification to the parameters. A complex model always has too many parameters that cannot be identified, and there may be parameter divergence problems. In order to solve this problem, this paper proposes a new equivalent circuit model, that is, the equivalent circuit model of the vehicle power battery based on the Auto Regression (AR) model. Based on this model, some inaccurate parameters were found in the parameter identification process, so a parameter identification method based on the extended Kalman filter algorithm and Recursive Least Squares (RLS) was used, and a composite model estimation method was used Comprehensive consideration of a series of restrictions such as State of Charge (SOC) limit and factory setting limit, combined with other methods such as equivalent circuit model, requires the estimated result to meet all the restrictions, to make up for some of the shortcomings of other methods, and make SOP estimation more accurate and reliable.
Defect analysis of the same batch of substation equipment based on big data analysis algorithm
Authors: Gao Qiang , Zhong Chuan , Wang Yong , Wang Peng , Yu Zaiming , Zhang Jiannan
Published: February 2021

High-quality power equipment is the basis for ensuring the safe operation of the power grid and improving the reliability of power supply. In actual operation, although some electrical equipment can continue to be used, abnormal operation or hidden dangers will affect the safety of people, equipment and power grid, reliable and economic operation of power grid and equipment, equipment output or life span, and power quality. Therefore, research on multi-dimensional analysis of the same batch of substation equipment, and identification of suspected family defects and frequent defects is of great significance for improving the company’s equipment management and defect management. The maturity and promotion of unstructured text data mining, graph computing technology, and semantic analysis have provided a wider dimensional space for the analysis of power equipment defect data. Aiming at the shortcomings of traditional defect data analysis, this article summarizes and analyzes the defects and hidden dangers found in the equipment, traces the distribution status of the same equipment through the physical “ID”, carries out multi-dimensional analysis of the same batch of equipment, and investigates the hidden dangers of equipment family defects. A big data analysis algorithm to build automatic identification models of suspected familial defects and frequent defects in main substation equipment such as transformers, disconnectors, circuit breakers, and use graph computing technology to quickly integrate analysis capabilities in multi-source heterogeneous data fusion with hidden relationship discovery capabilities, identify equipment defects with potential impact relationships. From historical data, discover which manufacturers or purchased batches of equipment are more likely to have the same defect, and which defect types have a higher frequency, improve the recognition model of family defects and frequent defects, and improve the accuracy and comprehensiveness of defect recognition.
Design and Implementation of a Capacitive Energy Storage Pulse Drive Source
Authors: Miao Weitong , Huang Jun , Chen Haitao , Wang Lei , Wang Yucheng
Published: February 2021

According to the requirement of driving power supply for pulsed semiconductor laser, a method of constant current output is proposed by combining large energy storage capacitance with MOS transistor working in linear region to solve the problem of generating high amplitude, short pulse width and high stability current pulse on low impedance load. The front stage uses the buck circuit to charge the energy storage capacitor, and through the hysteresis control of the buck circuit, the voltage of the energy storage capacitor is controlled. In the latter stage, the MOS transistor working in the linear region is used to realize the pulse output, and the PI module is used to adjust the output current to ensure the constant output current. Through PSPICE simulation, the key factors affecting the output pulse amplitude, pulse width and rise time are analyzed and verified by experiments. Using 155V DC power supply, the experimental results show that the capacitor energy storage pulse driver circuit can achieve a pulse constant current output with amplitude of 30A, pulse width of 300μs and rise time of less than 10μs on a 5 Ω low impedance load.
Quantitative Analysis of Generalized Suction on the Shear Strength of Unsaturated Soils
Authors: Sun Yu , Zhang Weichao
Published: February 2021

Taking the shear strength as the characteristic index to measure the strength of the soil, a characteristic parameter is established that can describe the contact distance between the surface of soil particles—the mean value of particle contact density. Using the indoor direct shear test of the preset scheme, the first-hand test data that three different factors such as moisture content, dry density and grain size quantitatively affect the shear strength of soil are obtained. Through the establishment of the quantitative relationship between the mean value of particle contact density and the shear strength, the theoretical description of the influence law that several key elements such as moisture content, void ratio, gradation, and particle size on the shear strength of unsaturated soil is realized, and the theoretical description and quantitative analysis of the influence of generalized suction on the shear strength of unsaturated soils are also completed.
Design of Coal Mine Power Grid Parameter Monitoring System Based on CAN Bus
Authors: Ma Yunlong
Published: February 2021

In order to ensure the safe production of coal mine enterprises, a real-time power grid parameter monitoring system is proposed by using modern computer and communication technology, so as to ensure the necessary power supply safety for the safe production of coal mines. Based on the analysis of coal mine safety production form and underground special operation environment, this paper introduces can communication technology and ECAN module in detail, designs the overall structure of coal mine power grid parameter monitoring system based on CAN bus, DSP minimum system, can interface circuit and software flow.
Study on the secondary plugging technology of drilling through the floor through drainage
Authors: Qin Muguang
Published: February 2021

According to the analysis and research results of the leakage channels of the boreholes in the coal mine face, the secondary plugging area of the leakage boreholes was determined, and the secondary plugging technology of “new extraction pipe + ‘one plug, one injection’” was formulated. And field test investigation was carried out. The research results show that after adopting the new secondary plugging technology for gas drainage, the concentration of gas drainage increases by 5~20 times, and the pure flow rate of gas drainage increases by 5~23 times, indicating that the drainage effect has improved significantly, which proves the feasibility of the secondary plugging technology.
Effects of Air Outlet Position and Air Speed on Airflow and Dust Field Distributions
Authors: Zhuang Xue’an
Published: February 2021

To meet the actual demands on ventilation and dust removal in mine heading faces and to reduce the potential safety threats and pollution risks of dust, this study investigates the migration and distribution trends of airflow and dust fields at different air outlet positions and air speeds under scenarios using forced ventilation and long-forced-short-exhaust ventilation techniques at the heading face under continuous mining operation, which is accomplished in the engineering context of Xiaobaodang Coal Mine by a combination of two-phase flow analysis and finite element simulation. As the results reveal, the return air speeds exhibit a “rising-falling-stable” trend at different air outlet positions and inlet air speeds. Appropriate increase of inlet air speed is effective in covering the front corner area and in improving the dust distribution in the roadway. Dust concentration on the return air side is markedly higher than on the air duct side, with distribution primarily in the front section. In the case of forced ventilation for the roadway having a large cross-sectional area of 22 m2, reasonable dust distribution on the return air side can be ensured when the air duct outlet is 10 m away from the front and the inlet air speed is 11 m/s. In the case of long-forced-short-exhaust ventilation, reasonable settings are a 15 m distance of air duct outlet from the front and a 9 m/s speed of inlet air.
Research on injection profile logging technology
Authors: Li Huiqiang
Published: February 2021

in this paper, through the analysis of the existing problems and influencing factors in the application of historical data of injection profile, continuous correlation logging technology of injection well, electromagnetic flow and tracer correlation logging technology are applied to solve the problems of overflow and contamination of isotope profile test in low injection wells. In general injection wells, the current collecting electromagnetic flow logging technology is applied; in stratified injection wells with different water injection intensity, oxygen activation logging, isotope water injection profile logging, tracer correlation logging and other logging technologies are used to combine logging according to the injection volume and string structure testing instrument scope, so as to eliminate the contamination effect and improve the accuracy of interval water injection profile test.
LUCC study under different geological conditions in Nanjiang district, Sichuan Province
Authors: Qu Shaodong , Li Yanan , Xiong Yufei
Published: February 2021

With the development of the times, more and more people begin to pay attention to land use change. This paper analyses the influence of different geological background conditions on the dynamic change of land use in Nanjiang County, Sichuan Province, and attempts to establish a land use model that meets the geological conditions of each region. According to different geological conditions, the purple soil of Cretaceous and Jurassic tilted single-sided low mountains and eroded terrace like narrow valley low mountains in the south is suitable for planting and breeding; the yellow soil of Jurassic and Triassic single-sided low and middle mountain purple soil in the middle is suitable for developing multi economic crops dominated by forest land; the limestone of yellow brown soil of Triassic, Sinian, Cambrian and middle mountain yellow soil in the north can be used for forestry and animal husbandry Industry.