bluuebunny/crossref_metadata_2025 huggingface dataset:
Physical and chemical activation mechanisms of carbon materials based on the microdomain model
Authors: Yang Inchan , Jung Meenkyoung , Kim Myung-Soo , Choi Dalsu , Jung Ji Chul
Published: April 2021

Activation mechanisms of carbon materials are proposed. Physical activation proceedsviaremoval of the carbon surface. Chemical activation produces highly porous carbon and enhances the crystallinity due to the removal of the non-graphitic parts.
A material of hierarchical interlayer-expanded MoS2 nanosheets/hollow N-doped carbon nanofibers as a promising Li+/Mg2+ co-intercalation host
Authors: Yu Xianbo , Zhao Guangyu , Liu Chao , Huang Huihuang , Shen Xiaojie , Zhang Naiqing
Published: April 2021

Interlayer-expanded MoS2 nanosheets/hollow N-doped carbon nanofibers were designed and exhibited superior electrochemical performances. More importantly, this electrode realizes Li+/Mg2+ co-intercalation into the host material even at 1000 mA g−1.
Controlling the gate dielectric properties of vinyl-addition polynorbornene copolymersviathiol–ene click chemistry for organic field-effect transistors
Authors: Kim Myung-Jin , Park Hyunjin , Ha Jinha , Thi Ho Linh Nguyet , Kim Eun Chae , Lee Woohwa , Park Sungmin , Won Jong Chan , Kim Dong-Gyun , Kim Yun Ho , Kim Yong Seok
Published: April 2021

The control of gate dielectric properties of vinyl-addition polynorbornene copolymers bearing pendant vinyl groups for OFET applications is demonstrated through photoinitiated thiol–ene click chemistry.
Optimising resource allocation for virtual network functions in SDN/NFV‐enabled MEC networks
Authors: Kiran Nahida , Liu Xuanlin , Wang Sihua , Yin Changchuan
Published: April 2021

Network function virtualisation (NFV), software defined networks (SDNs), and mobile edge computing (MEC) are emerging as core technologies to satisfy increasing number of users' demands in 5G and beyond wireless networks. SDN provides clean separation of the control plane from the data plane while NFV enables the flexible and on‐the‐fly creation and placement of virtual network functions (VNFs) and are able to be executed within the various locations of a distributed system. In this paper, VNF placement and resource allocation (VNFPRA) problem is considered which involves placing VNFs optimally in distributed NFV‐enabled MEC nodes and assigning MEC resources efficiently to these VNFs to satisfy users' requests in the network. Current solutions to this problem are slow and cannot handle real‐time requests. To this end, an SDN‐NFV infrastructure is proposed to tackle the VNFPRA problem in wireless MEC networks. Our aim is to minimise the overall placement and resource cost and also to minimise the total number of VNF migrations. A genetic based heuristic algorithm is proposed. The superior performance of the proposed solution is confirmed in comparison with four existing algorithms, i.e. resource utilisation‐single objective evolutionary algorithm (RU‐SOEA), genetic non‐bandwidth link allocation algorithm (GA‐NBA), random‐fit placement algorithm (RFPA), and first‐fit placement algorithm (FFPA). The results demonstrate that a coordinated placement of VNFs in SDN/NFV enabled MEC networks can satisfy the objective of overall reduced cost. Simulation results also reveal that the proposed scheme approximates well with the optimal solution returned by Gurobi and also achieves reduction on overall cost compared to other methods.
Flatness‐based control for steam‐turbine power generation units using a disturbance observer
Authors: Rigatos Gerasimos , Zervos Nikolaos , Siano Pierluigi , Wira Patrice , Abbaszadeh Masoud
Published: April 2021

Steam‐turbine power plants still supply a significant part of the electric power consumed worldwide. The viability of steam turbine power units depends on their efficiency to a great extent and the control method applied to the them is of major importance for achieving their improved functioning. The authors propose flatness‐based control and non‐linear Kalman Filtering for power generation units comprising synchronous generators connected to steam turbines. It is shown that the dynamic model of this power system is a differentially flat one. This property signifies that all its state variables and its control inputs can be expressed as its differential functions of selected state variables, the latter standing for the flat outputs of the system. This allows for its transformation into a linear canonical form in which the design of a feedback controller and the solution of the state estimation problem becomes possible. Moreover, by introducing a Kalman Filter‐based disturbance observer it becomes possible to identify in real time the perturbation terms that affect the power system's model. Through the proposed flatness‐based controller, fast and accurate tracking of all reference setpoints is achieved by the state vector elements of the power unit. Moreover, through the proposed Kalman Filter‐based disturbances estimator, the control loop is given additional robustness against modelling errors and external perturbations.
CPC‐GSCT: Visual quality assessment for coloured point cloud based on geometric segmentation and colour transformation
Authors: Hua Lei , Yu Mei , He Zhouyan , Tu Renwei , Jiang Gangyi
Published: April 2021

Coloured point cloud (CPC) is one of the important representations of three‐dimensional objects, which has been used in many fields. CPC may encounter geometric and colour distortion during its compression, simplification or other processing. Thus, the objective visual quality assessment of CPC is one of the urgent issues to be resolved in the CPC's applications. Aiming at this problem, this paper proposes a new full‐reference visual quality assessment metric for CPC based on geometric segmentation and colour transformation (CPC‐GSCT), which analyzes geometric distortion and colour distortion of CPC. First, considering the visual masking effect of CPC's geometric information, CPC is segmented into different regions and distributed with different weights to describe the influence of visual masking effect in CPC quality assessment. At the same time, a geometric combination feature vector is defined and extracted for measuring the CPC's geometric distortion. Then, considering the colour perception of human eyes, a colour combination feature vector is extracted to measure the CPC's colour distortion in HSV colour space. Finally, all the extracted geometric and colour features are constituted as a feature vector to predict the quality of CPC. Experimental results on three databases (IRPC, SJTU‐PCQA and CPCD2.0) show that the proposed CPC‐GSCT metric can achieve better performance in predicting the visual quality of CPC than relevant existing methods.
Joint likelihood estimation and model order selection for outlier censoring
Authors: Karbasi Seyed Mohammad
Published: April 2021

This study deals with the problem of outlier censoring from the secondary data in a radar scenario, where the number of outliers is unknown. To this end, a procedure consisting of joint likelihood estimation and statistical model order selection (MOS) is proposed. Since the maximum likelihood (ML) estimation of the outlier subset requires to solve a combinatorial problem, an approximate ML (AML) method is employed to reduce the complexity. Therefore, to determine the number of outliers, different MOS criteria based on likelihood function are applied. At the analysis stage, the performance of the proposed methods is assessed based on simulated data. The results highlight that the devised algorithms exhibit satisfactory performance with efficient complexity at the same time.
ESPRESSO mass determination of TOI-263b: an extreme inhabitant of the brown dwarf desert
Authors: Palle E. , Luque R. , Zapatero Osorio M. R. , Parviainen H. , Ikoma M. , Tabernero H. M. , Zechmeister M. , Mustill A. J. , Bejar V. S. J. , Narita N. , Murgas F.
Published: April 2021

The TESS mission has reported a wealth of new planetary systems around bright and nearby stars amenable for detailed characterizations of planet properties and atmospheres. However, not all interesting TESS planets orbit around bright host stars. TOI-263 b is a validated ultra-short-period substellar object in a 0.56-day orbit around a faint (V = 18.97) M 3.5 dwarf star. The substellar nature of TOI-263 b was explored using multicolor photometry: a true radius of 0.87 ± 0.21 RJ was determined, establishing TOI-263 b ’s nature as somewhere between an inflated Neptune and a brown dwarf. The orbital period-radius parameter space occupied by TOI-263 b is quite unique, which prompted a further characterization of its true nature. Here, we report radial velocity measurements of TOI-263 obtained with three VLT units and the ESPRESSO spectrograph to retrieve the mass of TOI-263 b. We find that TOI-263 b is a brown dwarf with a mass of 61.6 ± 4.0 MJup. Additionally, the orbital period of the brown dwarf is found to be synchronized with the rotation period of the host star, and the system is found to be relatively active, possibly revealing a star–brown dwarf interaction. All these findings suggest that the system’s formation history might be explained via disk fragmentation and a later migration to close-in orbits. If the system is found to be unstable, TOI-263 will be an excellent target to test the migration mechanisms before the brown dwarf becomes “engulfed” by its parent star.
A transmission spectrum of the planet candidate WD 1856+534 b and a lower limit to its mass
Authors: Alonso R. , Rodríguez-Gil P. , Izquierdo P. , Deeg H. J. , Lodieu N. , Cabrera-Lavers A. , Hollands M. A. , Pérez-Toledo F. M. , Castro-Rodríguez N. , Reverte Payá D.
Published: April 2021

The cool white dwarf WD 1856+534 was found to be transited by a Jupiter-sized object with a mass at or below 14 MJup. We used the GTC telescope to obtain and analyse the photometry and low-resolution spectroscopy of six transits of WD 1856+534 b, with the intention of deriving the slope of the transmission spectrum. Such a slope, assuming a cloud-free atmosphere dominated by Rayleigh scattering of the particles in its atmosphere, could be translated into an estimation of the mass of WD 1856+534 b. However, the resultant transmission spectrum is essentially flat and therefore permits only the determination of lower mass limits of 2.4 MJup at the 2σ level, or 1.6 MJup at 3σ. These limits have implications for some of the formation scenarios proposed for the object. We elaborate on the potential effects of clouds and hazes in our estimations, based on previous studies of Jupiter and Titan. In addition, we detected an Hα absorption feature in the combined spectrum of the host white dwarf, which leads to the assignation of a DA classification and allows the derivation of an independent set of atmospheric parameters. Furthermore, the epochs of five transits were measured with sub-second precision, which demonstrates that additional objects more massive than ≈5 MJup and with periods longer than O(100) days could be detected through the light-time effect.
Dynamic Spatial Model of Non-Domestic Waste Transport in Strategic Areas
Authors: Syahiya Minnaty , Noviar Megantara Erri , Husodo dan Teguh
Published: April 2021

The development of strategic areas that are taking place in several cities and districts in Indonesia is one of the solutions to the problem-solving approach instructed by the central government to develop the economy. However, along with the development of physical development and infrastructure in this strategic area, environmental problems began to emerge, especially solid waste. Increased community activity is one of the triggers for this increasing environmental problem. This research is a literature study that will answer the problem, what digital tools (applications / software) in a dynamic spatial model can support the final performance and what outputs can be obtained in its use. The method used is a qualitative method, research data is obtained from secondary data, several journals or articles that reveal about solid waste management. Data analysis was performed using descriptive analytical techniques. The mapping software application will simulate the determination of the location of waste collectors, visual representation of transportation routes, and optimization of transportation issues in order to provide economic and environmental benefits by reducing travel time, distance, fuel consumption, and pollutant emissions. The dynamic spatial model shows that the ArcGIS simulation results can be used as a strong basis for measuring the overall optimal route in solid waste management and dealing with dynamic changes in the future. Incorporating planning details on paper with real-world boundaries allows for realistic comparisons, for the application of sustainable environmental planning.
Utilization and Cultivation of Suweg (Amorphophallus paeoniifolius (Dennst.) Nicolson in Areas around Ciremai Mount, Cimanuk Watershed Region
Authors: Mutaqin A Z , Kurniadie D , Iskandar J , Nurzaman M , Husodo T
Published: April 2021

Amorphophallus paeoniifolius (Dennst.) Nicolson which in the local language is popularly known as suweg is a plant that grows widely in Indonesia, including in rural areas around Ciremai Mountain, whose landscape is in the Cimanuk Watershed area. This study aims to examine the knowledge of the population related to the utilization and cultivation of suweg in the Ciremai Mountain area, namely in the Cipulus, Cilancang, Jagasari, and Sindangpanji Village which are administratively included in Cikijing Sub District, Majalengka Regency, West Java Province. This study uses a qualitative method. The data was collected through deep interviews purposively with people who have competence as informants, including owners of the land where the suweg grows, farmers, and public figures. Data analysis was done by crosschecking, summarizing, and synthesizing descriptively narrated. As a result of the research, residents in the four villages informed that the suweg was already at least around 1950, but its exact origin is not known. Generally, suweg is used as jaburan, a type of additional food. Especially in Sindangpanji Village, suweg is also used as fish feed. People in the four villages do not cultivate suweg intensively. Suweg is also not a commodity, but only subsistence.
Carbon Sequestration Potentials of Man-made Grasslands under Different Pattern of Plantation Stands in West Bandung Regency, Indonesia
Authors: Dwitri Malik Annas , Isfahani Nurillah Maulida , Parikesit  , Withaningsih Susanti , Wingit Ratna
Published: April 2021

Alternatives of vegetations to store carbon need to be encouraged considering that forests are threatened by widespread destructions. One such vegetation is grasslands which have the potential for carbon storage and to reduce CO2 concentration in the atmosphere. At present, many enterprises have designed grasslands for many purposes. Grasslands at Cikalong Wetan and Little Farmers, West Bandung Regency were established under different pattern of plantation stands. The purpose of this research was to study the potential of carbon stock in grassland vegetation at these locations. Based on RaCSA method, the tree biomass was determined by nondestructive collection of density and basal area of trees, then calculated by an allometric equation. The ground cover biomass was determined by destructive collection of grass and roots. Total measured biomass was multiplied by 46% to obtain carbon storage. Based on the results, the potential of carbon stock in Little Farmers grassland (159,540 ton ha-1) is higher than in Cikalong Wetan (14,482 ton ha-1). Carbon stored in tree biomass gives the highest contribution to overall carbon stock potential in Little Farmers (94.84%) while carbon stored in below-ground understorey biomass gives the highest contribution in Cikalong Wetan (52.13 %). Different management of grasslands and pattern of plantation stands resulting a different contribution of carbon stock in every carbon pool. In order to maintain the carbon sequestration potentials of these locations, an agroforestry management such as agri-silviculture need to be encouraged. This study gives a comparison of the carbon sequestration potentials between two man-made grassland ecosystems. For many enterprises this study will aid in a management planning of man-made grassland in terms of ecosystem services, that is carbon sequestration.
Enhancing Extreme Weather Early Warning Systems in Upper Bekasi River Basin Through Coupled Hydro-meteorological Model
Authors: Mawardi Nizam , Asdak Chay , Hernandi Virgianto Rista
Published: April 2021

Flooding is frequently emerging events in the Upper Bekasi river basin and causes economic loss, property damage, loss of life, and even hinders sustainable development. Torrential rain is one of the natural hazards that often triggers flooding, especially in watersheds that have undergone land use changes. One of the mitigation efforts that can be carried out by the vicinity community, government, private enterprises and other stakeholders is by utilizing an early warning system. This study will delineate the successful use of coupled hydro-meteorological models to predict flooding in various regions of the world with different climatic and terrestrial characteristics. However, in order for an early warning system to be effective and improve community resilience, four vital elements of early warning systems are recommended to be fulfilled, namely risk knowledge, monitoring and warning services, dissemination and communication, and response capability. Therefore, this study will compile how coupled hydro-meteorological model is utilized properly to generate an effective early warning system so that thriving sustainability can be achieved.
Infektionen bei hämatologisch-onkologischen Patienten auf der Intensivstation
Authors: Kochanek Matthias , Böll Boris , Shimabukuro-Vornhagen Alexander , Eichenauer Dennis
Published: April 2021

Krebspatienten haben ein hohes Risiko, eine Infektion zu entwickeln, die eine Behandlung auf einer Intensivstation notwendig macht. Dies ist insbesondere bei hämatologischen Erkrankungen der Fall, da das Immunsystem fast immer am Krankheitsgeschehen beteiligt ist. Das Bild der Infektion kann mitunter sehr bunt sein, ist abhängig sowohl von der Primärerkrankung als auch der Krebstherapie und kann bis hin zum Vollbild einer Sepsis reichen.
The 16th Hilbert problem for discontinuous piecewise isochronous centers of degree one or two separated by a straight line
Authors: Esteban M. , Llibre J. , Valls C.
Published: April 2021

In this paper, we deal with discontinuous piecewise differential systems formed by two differential systems separated by a straight line when these two differential systems are linear centers (which always are isochronous) or quadratic isochronous centers. It is known that there is a unique family of linear isochronous centers and four families of quadratic isochronous centers. Combining these five types of isochronous centers, we obtain 15 classes of discontinuous piecewise differential systems. We provide upper bounds for the maximum number of limit cycles that these fifteen classes of discontinuous piecewise differential systems can exhibit, so we have solved the 16th Hilbert problem for such differential systems. Moreover, in seven of the classes of these discontinuous piecewise differential systems, the obtained upper bound on the maximum number of limit cycles is reached.
A planar microwave resonator with odd resonance for calibration in permanent moisture sensing applications
Authors: Olokede S. S. , Neyestanak M. L. , Chu Marco , Daneshmand M. , Naguib H. E.
Published: April 2021

A cylindrical dual-mode planar microwave ring resonator for a permanent moisture sensor is presented. The ring is design for TMn10 fundamental (odd-mode) resonance, and optimized to sustain stability (suitable for calibration reference against environmental interference) using Ansys high-frequency structure simulator. An even-mode resonance is perturbed by etching a step-impedance stub on the upper 0.5λ ring. The equations for the TMn10 mode resonance and its mode splitting are stated. The equivalent circuits of the ring, odd-, and even-modes are derived. The even-mode is set to capture the response of the permanent moisture withholding hydrophilic polyvinyl alcohol (PVA)–polyaniline (PANI) 0.26 mm-thick films. The in-lab made films are produced by infusing certain concentrations of PANI into pure PVA. On-spot measurements using a vector network analyzer (VNA) and time-based continuous data acquisitions using LabVIEW on NI PXIe–1075 VNA are done to confirm repeatability of the obtained results. A measured permanent moisture response of 180 MHz is confirmed for 50% PANI with a thickness (hfilm) of 0.55 mm. The sources of permanent moisture withholding capability of the films are investigated. Structural observation of the residue films, its permittivity changes, and morphological structural imagery confirmed the sources of permanent response.
New, improved analysis of correlation ECE data to accurately determine turbulent electron temperature spectra and magnitudes (invited)
Authors: Wang G. , Rhodes T. L. , Peebles W. A.
Published: April 2021

Turbulent electron temperature fluctuation measurement using a correlation electron cyclotron emission (CECE) radiometer has become an important diagnostic for studying energy transport in fusion plasmas, and its use is widespread in tokamaks (DIII-D, ASDEX Upgrade, Alcator C-Mod, Tore Supra, EAST, TCV, HL-2A, etc.). The CECE diagnostic typically performs correlation analysis between two closely spaced (within the turbulent correlation length) ECE channels that are dominated by uncorrelated thermal noise emission. This allows electron temperature fluctuations embedded in the thermal noise to be revealed and fluctuation level and spectra determined. We have demonstrated a new, improved CECE coherency-based analysis for calculating the temperature fluctuation frequency spectrum and level, which has been verified both numerically through the simulation of synthetic ECE radiometer data and through analysis of experimental data from the CECE system on DIII-D. The new formulation places coherency-based analysis on a firm foundational footing and corrects some currently published methodologies. This new method accurately accounts for bias error in the coherence function and correctly calculates noise levels for a fixed data record length. It provides excellent accuracy in determining temperature fluctuation level (e.g., <10% error) even for a small realization number in the ensemble average. The method also has a smaller uncertainty (i.e., error bar) in the power spectrum when compared to the more standard cross-power method when evaluated at low coherency. Direct calculation of system noise level using correlation between randomized intermediate frequency signals is recommended.
Strain-modulated magnetization precession in skyrmion-based spin transfer nano-oscillator
Authors: Yu Guoliang , Xu Xiaofei , Qiu Yang , Yang Han , Zhu Mingmin , Zhou Haomiao
Published: April 2021

The magnetic skyrmion-based spin transfer nano-oscillators have been set as microwave signal emitters and gaining in popularity due to their performance and integrability in the existing CMOS process flow. In this work, we report our investigations on the strain-modulated magnetization precession in the breathing mode skyrmion-based spin transfer nano-oscillator, which strains from the juxtaposed piezoelectric materials. The strain-modulated skyrmion breathing frequency can be strongly controlled by biaxial-isotropy in-plane strain, in which the tunable range varies from 500 MHz to 7 GHz under the fixed current density −4 ×1012 A/m2 and varying strain from −2000 ppm to 4000 ppm. Such tunability is external magnetic free and even does not reduce the dynamic resistance variation. Through this method, a promising digital binary frequency shift-key and amplitude shift-key modulation technique are presented, in which the magnetization precession frequency and amplitude can be tuned with the co-action of current and strain pulses. These findings are providing an optional route to design future tunable spin transfer nano-oscillators based on skyrmion with better performance in the wireless communication.
Quantum computation of dominant products in lithium–sulfur batteries
Authors: Rice Julia E. , Gujarati Tanvi P. , Motta Mario , Takeshita Tyler Y. , Lee Eunseok , Latone Joseph A. , Garcia Jeannette M.
Published: April 2021

Quantum chemistry simulations of some industrially relevant molecules are reported, employing variational quantum algorithms for near-term quantum devices. The energies and dipole moments are calculated along the dissociation curves for lithium hydride (LiH), hydrogen sulfide, lithium hydrogen sulfide, and lithium sulfide. In all cases, we focus on the breaking of a single bond to obtain information about the stability of the molecular species being investigated. We calculate energies and a variety of electrostatic properties of these molecules using classical simulators of quantum devices, with up to 21 qubits for lithium sulfide. Moreover, we calculate the ground-state energy and dipole moment along the dissociation pathway of LiH using IBM quantum devices. This is the first example, to the best of our knowledge, of dipole moment calculations being performed on quantum hardware.
Telecom InP-based quantum dash photodetectors grown on Si
Authors: Xue Ying , Wang Yi , Luo Wei , Huang Jie , Lin Liying , Tsang Hon Ki , Lau Kei May
Published: April 2021

Photodetectors on Si with high responsivity, large bandwidth, and multispectral operation are required for high data rate communications using Si photonics. We report characteristics of InP-based quantum dash (QDash) photodetectors with a p-i-n structure directly grown on (001) Si. Three layers of quantum dashes were grown on InP on Si templates and fabricated into waveguide photodetectors. The QDash photodetectors can operate from 1240 nm to 1640 nm, covering the entire telecommunication band. A low dark current density of 2.1 × 10−6 A/cm2, responsivities of 0.35 ± 0.05 A/W at 1550 nm and 0.94 ± 0.05 A/W at 1310 nm, and a 3-dB bandwidth of 10.3 GHz were demonstrated. Our results show that the QDash photodetectors grown on Si hold great potential for on-chip integration in Si-photonics.
Improved delayed detached-eddy simulation and proper orthogonal decomposition analysis of turbulent wake behind a wall-mounted square cylinder
Authors: Yousif Mustafa Z. , Lim HeeChang
Published: April 2021

The turbulent flow past a wall-mounted square cylinder with an aspect ratio of 4 was investigated with the aid of Spalart–Allmaras improved delayed detached-eddy simulation and proper orthogonal decomposition (POD) analysis. The Reynolds number was equal to 12 000 (based on the free-stream velocity and obstacle width). The boundary layer thickness was ∼0.18 of the obstacle height. This study focused on analyzing the vortical structure of the wake and vortex shedding process along the obstacle height. A quantitative comparison of the first- and second-order flow statistics with the available experimental and direct numerical simulation data was used to validate the numerical results. The numerical model coupled with the vortex method of generating the turbulent inflow conditions could successfully reproduce the flow field around and behind the obstacle with commendable accuracy. The flow structure and vortex shedding characteristics near the wake formation region were discussed in detail using time-averaged and instantaneous flow parameters obtained from the simulation. Dipole type mean streamwise vortices and half-loop hairpin instantaneous vortices with energetic motions were identified. A coherent shedding structure was reported along the obstacle using two-point correlations. Two types of vortex shedding intervals were identified, namely, low amplitude fluctuations (LAFs) and high amplitude fluctuations (HAFs) [P. Sattari et al., Exp. Fluids 52, 1149–1167 (2012)]. The HAFs’ interval exhibits von Kármán-like behavior with a phase difference of ∼180°, while the LAFs’ interval shows less periodic behavior. It was observed that the effect of the LAFs’ interval tends to weaken the alternating shedding along the obstacle height. The POD analysis of the wake showed that for the elevations between 0.25 and 0.5 of the obstacle height, the first two POD modes represent the alternating shedding and contribute to 66.6%–57.6% of the total turbulent kinetic energy. However, at the free end of the obstacle, the first two modes have a symmetrical shedding nature and share 36.5% of the kinetic energy, while the rest of the energy is distributed between the alternating and the random shedding processes. A simple low-order model based on the vortex-shedding phase angle and the spectrum of the time coefficients obtained from POD was developed to predict the wake dynamics at the range of elevations where the alternating shedding is dominated.
Formulation of stochastic contact Hamiltonian systems
Authors: Wei Pingyuan , Wang Zibo
Published: April 2021

In this work, we devise a stochastic version of contact Hamiltonian systems and show that the phase flows of these systems preserve contact structures. Moreover, we provide a sufficient condition under which these stochastic contact Hamiltonian systems are completely integrable. This establishes an appropriate framework for investigating stochastic contact Hamiltonian systems.
Multi-frequency coherent emission from superstructure thermal emitters
Authors: Lu Guanyu , Tadjer Marko , Caldwell Joshua D. , Folland Thomas G.
Published: April 2021

Long-range spatial coherence can be induced in incoherent thermal emitters by embedding a periodic grating within a material supporting propagating polaritons or dielectric modes. However, only a single spatially coherent mode is supported by purely periodic thermal emitters. While various designs have been proposed for the purpose of allowing arbitrary emission profiles, the limitations associated with the partial spatial coherence of thermal emitters are not known. Here, we explore superstructure gratings (SSGs) to control the spatial and spectral properties of thermal emitters. SSGs have long-range periodicity but employ a unit cell that provides multiple Bragg vectors to interact with light. These Bragg vectors allow simultaneous launching of polaritons with different frequencies/wavevectors in a single grating, manifesting as additional spatial and spectral modes in the thermal emission profile. However, SSGs still have a well-defined period, which allows us to assess the role that finite spatial coherence plays in thermal emitters. We find that the spatial coherence length defines the maximum possible SSG period that can be used. This provides a fundamental limit on the degree of spatial coherence that can be induced in a thermal emitter and has broader implications for the use of techniques such as inverse design for structure optimization.
Highly efficient and stable electroluminescence from Er-doped Ga2O3 nanofilms fabricated by atomic layer deposition on silicon
Authors: Yang Li , Xu Jing , Yuan Kang , Yang Yang , Sun Jiaming
Published: April 2021

Intense 1.53 μm electroluminescence (EL) is achieved from metal-oxide-semiconductor light-emitting devices based on Er-doped Ga2O3 (Ga2O3:Er) nanofilms fabricated by atomic layer deposition. Due to the wide bandgap and outstanding tolerance to electric field and electron injection of the amorphous Ga2O3 matrix, these silicon-based devices present a low turn-on voltage of ∼15 V, while the maximum injection current can reach 5 A/cm2. The optical power density of the EL emissions is improved to 23.73 mW/cm2, with the external quantum efficiency of 36.5% and power efficiency of 0.81%. The prototype devices show good stability and retain ∼90% initial EL intensity after operating consistently for 100 h. The EL originates from the impact excitation of doped Er3+ ions by hot electrons generated within dielectric layers. This work manifests the potential of fabricating practical Si-based light source from Ga2O3:Er nanofilms, enabling various optoelectronic applications.
Dead clades walking are a pervasive macroevolutionary pattern
Authors: Barnes B. Davis , Sclafani Judith A. , Zaffos Andrew
Published: April 2021

Significance

“Dead clade walking” refers to fossil groups that suffer major drops in their biodiversity at a mass extinction but do not completely disappear from the fossil record. Why these groups were able to survive but not rediversify remains a relative mystery. Controls on the timing of their eventual extinction are additionally unclear. By gauging the frequency and cause of dead clades walking, we may be able to better understand how mass extinction events have shaped the evolution of animal lineages over Earth history.
Genomic stability through time despite decades of exploitation in cod on both sides of the Atlantic
Authors: Pinsky Malin L. , Eikeset Anne Maria , Helmerson Cecilia , Bradbury Ian R. , Bentzen Paul , Morris Corey , Gondek-Wyrozemska Agata T. , Baalsrud Helle Tessand , Brieuc Marine Servane Ono , Kjesbu Olav Sigurd , Godiksen Jane A. , Barth Julia M. I. , Matschiner Michael , Stenseth Nils Chr. , Jakobsen Kjetill S. , Jentoft Sissel , Star Bastiaan
Published: April 2021

Significance

Both theory and experiments suggest that fishing can drive the evolution of an earlier maturation age. However, determining whether changes in the wild are the result of fisheries-induced evolution has been difficult. Temporal, genome-wide datasets can directly reveal responses to selection. Here, we investigate the genomes of two wild Atlantic cod populations from samples that pre- and postdate periods of intensive fishing. Although phenotypic changes suggest fisheries-induced evolution, we do not find evidence for any strong genomic change or loss of genetic diversity. While evolution could have occurred through undetectable frequency changes at many loci, the irreversible loss of late-maturing genotypes appears unlikely. Instead, we suggest that recovery of former phenotypes is possible with reduced fishing pressure.
Vulpia myuros (annual fescue).
Authors: Weber Ewald
Published: April 2021

Vulpia myuros is an annual grass, native to much of Europe and parts of Asia, introduced to the USA, Australia and a number of other countries, and reported as invasive in Australia, the western USA and parts of the Pacific. It out competes native species in grasslands of the western US and is a significant agricultural weed. It forms dense swards and its shallow roots suppress growth of native grasses and forbs. Establishment of native plants is strongly hindered once it has become dominant; because it is a winter-annual, it grows rapidly in early spring, thus successfully competing with the slower-growing native perennial grasses. It is a problem weed in pastures and in direct-seed cropping systems. Infested hay can cause injury to livestock due to the sharp seeds. Seeds easily attach to animals and cause losses in the wool industry. Residues of degrading Vulpia plants affect growth of other species including crops.
Ceratitis rosa (Natal fruit fly).
Authors: De Meyer Marc
Published: April 2021

C. rosa is a polyphagous African species. Its known distribution is mainly southern and eastern Africa. It is considered to be a major pest of a number of commercial fruits, including fruits that are grown in subtropical or more temperate environments (but see remark under host plants). It has similar environmental requirements to Ceratitis capitata except that it can withstand less dry conditions. It should be considered as a potential invasive species in other parts of Africa, outside its current range, and in other parts of the world (Tanga et al., 2018). The most likely pathway of dispersal and introduction is as larvae in infested fruits with commercial shipments or in the luggage of travellers. C. rosa is of quarantine significance for EPPO, JUNAC and OIRSA.
Chilo suppressalis (striped rice stem borer).
Authors: Maes Koen
Published: April 2021

This is one of the most important pests of rice in East Asia, India and Indonesia. In East Asia, C. suppressalis occurs together with Chilo hyrax and Chilo christophi. This pest was probably introduced in Spain and Hawaii by humans (Bleszynski, 1970). It is now also present in the Northern Territory of Australia. The species tolerates low to very low temperatures and is therefore present in temperate and subtropical Asia. This low temperature tolerance enables it to adapt to other regions. The fact that C. suppressalis has become established in France, Spain and Portugal indicates the potential for long-distance movements and there would seem to be a real danger that it could be introduced into Africa, or other ecologically favourable areas.
Pelopidas mathias (rice skipper).
Authors: Cock Matthew
Published: April 2021

Due to its wide host range and low reproductive potential, colonization rates of P. mathias are rather low compared to more specialized rice pests. Those ovipositing adults that do arrive do so after significant numbers of natural enemies have built up; this helps to explain the normally low pest status of P. mathias.
Acacia auriculiformis (northern black wattle).
Authors: Vélez-Gavilán Jeanine
Published: April 2021

Few other species can match the ability of A. auriculiformis to grow on harsh sites in the tropics. Its rapid early growth rate, ability to fix nitrogen, tolerance of infertile, acid, alkaline, saline or seasonally waterlogged soils and moderate dry seasons make it a useful species for the rehabilitation of degraded lands. It has been widely planted for fuelwood production, erosion control, ornament or shade mainly in Asia, but also in Africa and South America. The stem form can be improved significantly by selection and breeding, providing outstanding prospects for industrial plantations to produce paper pulp and other timber products.
Pterocarpus macrocarpus (Burma padauk).
Authors: Rojas-Sandoval Julissa
Published: April 2021

P. macrocarpus is a medium to large (usually up to 25 m tall, but sometimes up to 35 m tall) tree native to Myanmar, northern Thailand, Cambodia, Laos and Vietnam. It is a light-demanding, frost sensitive species, and natural regeneration is generally best in dry, open forest, and in disturbed areas. In its native range it grows best on sandy loams (Hundley, 1957). In Puerto Rico, it has grown well on soils ranging from sandy loams to well-drained clays (Francis, 1989). A volume table is available for a trial plantation in Laos; trees had attained an average height of 14.5 m after 13 years (Hjelm, 1995). Although small trees coppice well, coppicing ability declines with size.
Signature of universal fast scrambling in the transient response of a driven mott insulator system
Authors: Kumar Sanjeev , Tripathi Vikram
Published: April 2021

The scrambling rate λ
s, a measure of the early growth of decoherence in an interacting quantum system, has been conjectured to have a universal saturation bound, λ
s ⩽ 2πk
B
T/ℏ, where T is the temperature. This decoherence arises from the spread of quantum information over a large number of untracked degrees of freedom. The commonly studied indicator of scrambling is the out of time-ordered correlator (OTOC) of noncommuting quantum operators, in-turn related to generalized uncertainty relations, and reminiscent of the Lyapunov exponent of classically chaotic systems. From a practical measurement point of view, other quantities besides OTOCs, that are also sensitive to these generalized uncertainty relations, may capture the scrambling behavior. Here, using a large-

N

Keldysh field theory approach, we show that the nonequilibrium current response of a Mott insulator system consisting of a mesoscopic quantum dot array, when subjected to an electric field quench, reveals this phenomenon on account of number-phase uncertainty. Both ac and dc field quenches are considered. The passage from the initial Mott insulator phase with well-defined charge excitations, to the final nonequilibrium steady current state, is revealed in the transient current response that has Bloch-like oscillations. We find that the amplitude of these oscillations decreases at the universal rate, 2πk
B
T/ℏ, associated with fast scramblers. Our Mott insulator model provides a new example of a fast scrambler in addition to the known ones such as extremal black holes and the Sachdev–Ye–Kitaev (SYK) model.
Magnetic ordering in the Ising antiferromagnetic pyrochlore Nd2ScNbO7
Authors: Mauws C , Hiebert N , Rutherford M L , Zhou H D , Huang Q , Stone M B , Butch N P , Su Y , Choi E S , Yamani Z , Wiebe C R
Published: April 2021

The question of structural disorder and its effects on magnetism is relevant to a number of spin liquid candidate materials. Although commonly thought of as a route to spin glass behaviour, here we describe a system in which the structural disorder results in long-range antiferromagnetic order due to local symmetry breaking. Nd2ScNbO7 is shown to have a dispersionless gapped excitation observed in other neodymium pyrochlores below T
N = 0.37 K through polarized and inelastic neutron scattering. However the dispersing spin waves are not observed. This excited mode is shown to occur in only 14(2)% of the neodymium ions through spectroscopy and is consistent with total scattering measurements as well as the magnitude of the dynamic moment 0.26(2) μ

B
. The remaining magnetic species order completely into the all-in all-out Ising antiferromagnetic structure. This can be seen as a result of local symmetry breaking due disordered Sc+3 and Nb+5 ions about the A-site. From this work, it has been established that B-site disorder restores the dipole-like behaviour of the Nd+3 ions compared to the Nd2B2O7 parent series.
A sliding window method to identify defects in 3D printing lattice structure based on the difference principle
Authors: Wen Yintang , Fu Kai , Li Yongbao , Zhang Yuyan
Published: April 2021

Structural defects are inevitably produced by residual stress in the 3D printing process, which reduce the structural-functional properties. For a typical 3D printing lattice structure, a new sliding window approach to intelligently identify defects, based on the difference principle, in the inspection process was proposed. Industrial computed tomography (CT) was used for image information acquisition. The grayscale standard deviation in the local range of the CT slice is calculated to characterize the grayscale variation of the defect location. On this basis, a sliding window method is proposed for traversing CT slices. Three different sizes of window and the corresponding calculation methods were established, and then the appropriate window was selected through comparison. After differential processing is performed on the traversed image to extract the defect feature, automatic defect recognition rules are created. The experimental results show that the recognition rate of the proposed method is 98.5% for typical internal defects of metal 3D lattice structures and the validity of the method is verified. Compared with a manual marking method, this method can effectively improve the efficiency of defect detection.
Combined adaptive robust Kalman filter algorithm
Authors: Lin Xu , Li Wei , Li Shaoda , Ye Jiang , Yao Chaolong , He Zhijie
Published: April 2021

The precise positioning of dynamic and static objects such as vehicles and pedestrians is a key technology. A global navigation satellite system signal is the primary signal source required to achieve precise positioning, and the optimal estimation method used in precise positioning is Kalman filtering (KF). Standard KF can only achieve optimal estimation results under the conditions that the mathematical model has been determined and the noise characteristics are known. However, when there are measurement outliers and prior noise information deviations, the accuracy of KF cannot be guaranteed. To effectively solve the above problems, a combined adaptive robust Kalman filter (CARKF) algorithm is proposed. First, the influence of measurement outliers on KF accuracy is resisted using the robust Kalman filter method. Then, the influence of an anomalous innovation on its autocorrelation sequence and cross-correlation sequence is resisted by the robust estimator for correlated observations based on the IGGIII method, to ensure the correct estimation of the correlation function sequence of the filtered innovation statistics. Finally, the autocovariance least-squares method is used to eliminate the coupling effect between noise covariances and accurately estimate the unknown noise covariance information. Moreover, an iterative strategy is adopted to eliminate the effect of errors caused by prior noise covariance deviations. The results of the three experiments show that the CARKF method can not only effectively resist the influence of measurement outliers on filtering accuracy and noise covariance valuation but also overcome the influence of errors caused by prior noise deviations and accurately simultaneously estimate two kinds of unknown noise covariance information.
Nonlinear feedback algorithm for tearing-mode magnetic control in tokamak
Authors: Ivanov N V , Kakurin A M
Published: April 2021

Results of calculations and analysis of the tearing-mode evolution under the effect of resonant magnetic perturbation produced by a nonlinear feedback system in rotating tokamak plasma are presented. The TEAR-code used for calculations is based on the visco-resistive magnetohydrodynamic approximation that gives coupled diffusion-type equations for the magnetic flux perturbation and for the plasma rotation velocities in toroidal and poloidal directions. The code is supplemented by a computational unit simulating the nonlinear algorithm of the feedback system. The feedback gain and phase shift are automatically regulated in real time. The gain depends on the tearing-mode amplitude. At high feedback input signals, the gain does not exceed some finite value to reduce technical requirements for the feedback actuator and to mitigate the phase instability. In the process of the tearing-mode suppression, the gain gradually increases to provide the mode control under reduction of feedback input signal and rise of the intrinsic tearing-mode stability index. Besides that, the real-time control of the feedback phase shift is provided to additionally mitigate the phase instability. According to simulation, the used nonlinear characteristics of the feedback algorithm improve the efficiency of the tearing-mode suppression.
Characteristics of neutron emission profile from neutral beam heated plasmas of the Large Helical Device at various magnetic field strengths
Authors: Ogawa K , Isobe M , Sugiyama S , Spong D A , Sangaroon S , Seki R , Nuga H , Yamaguchi H , Kamio S , Fujiwara Y , Kobayashi M I , Jo J , Osakabe M
Published: April 2021

The neutron emission profile of deuterium plasma in the Large Helical Device was measured with a multi-sightline vertical neutron camera under various magnetic field strength conditions. It was found that the line-integrated neutron emission profile shifts outward in the co-neutral beam (NB) case and inward in the counter NB case. Here, co- and counter directions correspond to enhance and reduce the poloidal magnetic field directions, respectively. The shift becomes more significant when the magnetic field decreased in strength. The experimentally obtained neutron emission profile was compared with the orbit-following models simulated through the DELTA5D code. The calculated neutron emission profiles vary according to the magnetic field strength because of the change of beam ion orbit and the slowing down due to the plasma parameter changes. Although a relatively narrow profile was obtained in the calculations at the inboard side for the co-NB case in the relatively low field condition, the profiles obtained through calculation and experiment were almost qualitatively aligned.