bluuebunny/crossref_metadata_2025 huggingface dataset:
Y–F co-doping behavior of LiFePO4/C nanocomposites for high-rate lithium-ion batteries
Authors: Wang Hongqiang , Lai Anjie , Huang Dequan , Chu Youqi , Hu Sijiang , Pan Qichang , Liu Zhiheng , Zheng Fenghua , Huang Youguo , Li Qingyu
Published: February 2021

Lithium iron phosphate (LFP) has become one of the current mainstream cathode materials due to its high safety and low price.
Evolution of low-dimensional material-based field-effect transistors
Authors: Ahmad Waqas , Gong Youning , Abbas Ghulam , Khan Karim , Khan Maaz , Ali Ghafar , Shuja Ahmed , Tareen Ayesha Khan , Khan Qasim , Li Delong
Published: February 2021

The recent research progress on low-dimensional material-based FETs, including their classification and applications, has been reviewed.
Driving magnetic domains at the nanoscale by interfacial strain-induced proximity
Authors: Valmianski Ilya , Rodríguez Arantxa Fraile , Rodríguez-Álvarez Javier , García del Muro Montserrat , Wolowiec Christian , Kronast Florian , Ramírez Juan Gabriel , Schuller Ivan K. , Labarta Amílcar , Batlle Xavier
Published: February 2021

Temperature-driven reorientation of magnetic domains in a thin Ni film across the structural phase transition of promixity-coupled V2O3layer, giving rise to large chances in the magnetic anisotropy of the Ni film, of relevance for straintronics.
Boosting the sensing properties of resistive-based gas sensors by irradiation techniques: a review
Authors: Majhi Sanjit Manohar , Mirzaei Ali , Navale Sachin , Kim Hyoun Woo , Kim Sang Sub
Published: February 2021

The ongoing need to detect and monitor hazardous, volatile, and flammable gases has led to the use of gas sensors in several fields to improve safety and health issues.
A tumor-activatable peptide supramolecular nanoplatform for the delivery of dual-gene targeted siRNAs for drug-resistant cancer treatment
Authors: Wu Yahui , Zhong Dan , Li Yunkun , Wu Huayu , Zhang Hu , Mao Hongli , Yang Jun , Luo Kui , Gong Qiyong , Gu Zhongwei
Published: February 2021

Combinatorial short interference RNA (siRNA) technology for the silencing of multiple genes is expected to provide an effective therapeutic approach for cancer with complex genetic mutation and dysregulation.
Construction of a Pd(PdO)/Co3O4@SiO2 core–shell structure for efficient low-temperature methane combustion
Authors: Ma Yongde , Li Shusheng , Zhang Tianhua , Zhang Yangyu , Wang Xiuyun , Xiao Yihong , Zhan Yingying , Jiang Lilong
Published: February 2021

A Pd–Co bimetallic oxide catalyst with a core–shell structure which shows excellent activity in methane combustion is demonstrated.
A dentin hypersensitivity treatment using highly stable photothermal conversion nanoparticles
Authors: Gao Heqi , Zhang Lanrui , Lian Xiaoli , Wang Yue , Jiang Shihui , Wang Guanhua , Dai Xiaohua , Zou Huiru , Ding Dan
Published: February 2021

A type of photothermal biocompatible organic nanoparticles with a high PCE (40.6%) was developed and investigated, followed by the achievement of a significantly more effective phototheranostic dental hypersensitivity treatment combined with laser.
Hydrogel-derived luminescent scaffolds for biomedical applications
Authors: Yang Yujiao , Zhang Yang , Xie Sheng , Tang Youhong , Zeng Zebing , Tang Ben Zhong
Published: February 2021

We provide a review on how luminescence functionality can be integrated with modifiable hydrogels to extend the frontiers of luminescent materials for health technologies.
Mode of inhibitory binding of epigallocatechin gallate to the ubiquitin-activating enzyme Uba1 via accelerated molecular dynamics
Authors: Gaur Paras , Fenteany Gabriel , Tyagi Chetna
Published: February 2021

The hinge-like movement of the SCCH domain upon ligand binding closes the ubiquitin binding site and disrupts the interfaces crucial for thioester bond formation.
On-line separation/analysis of Rhodamine B dye based on a solid-phase extraction high performance liquid chromatography self-designed device
Authors: Wu Jun , Liu Wei , Zhu Rui , Zhu Xiashi
Published: February 2021

A special self-designed device based on poly-1-vinyl-3-pentylimidazole hexafluorophosphate (PILs-C5) solid-phase extraction and high performance liquid chromatography (HPLC) is proposed as a novel method for the on-line separation and analysis of Rhodamine B (RhB) dye.
All-in-one: a new approach toward robust and solution-processable copper halide hybrid semiconductors by integrating covalent, coordinate and ionic bonds in their structures
Authors: Hei Xiuze , Li Jing
Published: February 2021

This Perspective features the newly emerged AIO-type Cu(i)X-based hybrid semiconductors and showcases their structural diversity, solution-processability, framework stability, important photophysical properties and related potential applications.
Elastin-inspired supramolecular hydrogels: a multifaceted extracellular matrix protein in biomedical engineering
Authors: Sharma Archita , Sharma Pooja , Roy Sangita
Published: February 2021

The phenomenal advancement in regenerative medicines has led to the development of bioinspired materials to fabricate a biomimetic artificial extracellular matrix (ECM) to support cellular survival, proliferation, and differentiation.
The crystal structure and electrical/thermal transport properties of Li1−xSn2+xP2and its performance as a Li-ion battery anode material
Authors: Goto Yosuke , Nakanishi Shota , Nakai Yusuke , Mito Takeshi , Miura Akira , Moriyoshi Chikako , Kuroiwa Yoshihiro , Usui Hidetomo , Matsuda Tatsuma D. , Aoki Yuji , Nakacho Yoshifumi , Yamada Yuto , Kanamura Kiyoshi , Mizuguchi Yoshikazu
Published: February 2021

The physical and chemical properties of Li1−xSn2+xP2are affected by Li/Sn mixed occupation with local ordering.
Monolayer InSe photodetector with strong anisotropy and surface-bound excitons
Authors: Gao Siyan , Liu Liang , Wen Bo , Zhang Xi
Published: February 2021

NEGF-DFT and TD-DFT calculations show that surface-bound excitons mainly give rise to the strong anisotropic photocurrent in a monolayer InSe photodetector.
Site-selective protonation of the one-electron reduced cofactor in [FeFe]-hydrogenase
Authors: Laun Konstantin , Baranova Iuliia , Duan Jifu , Kertess Leonie , Wittkamp Florian , Apfel Ulf-Peter , Happe Thomas , Senger Moritz , Stripp Sven T.
Published: February 2021

Hydrogenases are bidirectional redox enzymes that catalyze hydrogen turnover in archaea, bacteria, and algae.
Anion photoelectron spectroscopy and quantum chemistry calculations of TaSi16−/0 clusters: global minimum fullerene-like cage structure, bonding and superatom properties
Authors: Lu Sheng-Jie
Published: February 2021

TaSi16− has a fullerene-like cage structure, σ + π double delocalized bonding patterns, a superatom closed-shell electron configuration, and aromaticity.
Pd-N-heterocyclic carbene complex catalysed C–H bond activation of 2-isobutylthiazole at the C5 position with aryl bromides
Authors: Khan Siraj , Buğday Nesrin , Yaşar Sedat , Ullah Naseem , Özdemir İsmail
Published: February 2021

An effective and efficient catalytic system has been reported for the synthesis of C5-arylated 2-isobutylthiazoles.
Structural characterisation of natural products by means of quantum chemical calculations of NMR parameters: new insights
Authors: Costa Fabio L. P. , de Albuquerque Ana C. F. , Fiorot Rodolfo G. , Lião Luciano M. , Martorano Lucas H. , Mota Gunar V. S. , Valverde Alessandra L. , Carneiro José W. M. , dos Santos Junior Fernando M.
Published: February 2021

In this review, we focus in all aspects of NMR simulation of natural products, from the fundamentals to the new computational toolboxes available, combining advanced quantum chemical calculations with upstream data processing and machine learning.
Design, synthesis, and properties of a six-membered oligofuran macrocycle
Authors: Varni Anthony J. , Kawakami Manami , Tristram-Nagle Stephanie A. , Yaron David , Kowalewski Tomasz , Noonan Kevin J. T.
Published: February 2021

In this report, the synthesis and properties of an ester-functionalized macrocyclic sexifuran (C6FE) are presented.
Bottom-up fabrication of triazine-based frameworks as metal-free materials for supercapacitors and oxygen reduction reaction
Authors: Cao Ronghan , Hu Fangyuan , Zhang Tianpeng , Shao Wenlong , Liu Siyang , Jian Xigao
Published: February 2021

A series of N, O co-doped materials were prepared by a facile method and applied in both supercapacitors and the ORR.
Examining the electron transport in chalcogenide perovskite BaZrS3
Authors: Osei-Agyemang Eric , Koratkar Nikhil , Balasubramanian Ganesh
Published: February 2021

Orthorhombic BaZrS3 is a potential optoelectronic material with prospective applications in photovoltaic and thermoelectric devices.
E3 ubiquitin ligase-mediated regulation of vertebrate ocular development; new insights into the function of SIAH enzymes
Authors: Piedade Warlen Pereira , Famulski Jakub K.
Published: February 2021

Developmental regulation of the vertebrate visual system has been a focus of investigation for generations as understanding this critical time period has direct implications on our understanding of congenital blinding disease. The majority of studies to date have focused on transcriptional regulation mediated by morphogen gradients and signaling pathways. However, recent studies of post translational regulation during ocular development have shed light on the role of the ubiquitin proteasome system (UPS). This rather ubiquitous yet highly diverse system is well known for regulating protein function and localization as well as stability via targeting for degradation by the 26S proteasome. Work from many model organisms has recently identified UPS activity during various milestones of ocular development including retinal morphogenesis, retinal ganglion cell function as well as photoreceptor homeostasis. In particular work from flies and zebrafish has highlighted the role of the E3 ligase enzyme family, Seven in Absentia Homologue (Siah) during these events. In this review, we summarize the current understanding of UPS activity during Drosophila and vertebrate ocular development, with a major focus on recent findings correlating Siah E3 ligase activity with two major developmental stages of vertebrate ocular development, retinal morphogenesis and photoreceptor specification and survival.
Constraint programing for solving four complex flexible shop scheduling problems
Authors: Meng Leilei , Lu Chao , Zhang Biao , Ren Yaping , Lv Chang , Sang Hongyan , Li Junqing , Zhang Chaoyong
Published: February 2021

In recent years, with the advent of robust solvers such as Cplex and Gurobi, constraint programing (CP) has been widely applied to a variety of scheduling problems. This paper presents CP models for formulating four scheduling problems with minimal makespan and complex constraints: the no‐wait hybrid flow shop scheduling problem, the hybrid flow shop scheduling problem with sequence‐dependent setup times, the flexible job shop scheduling problem with worker flexibility and the semiconductor final testing problem. The advantages of CP method in solving these four complex scheduling problems are explored. Finally, a set of benchmark instances are adopted to demonstrate the effectiveness and efficiency of the CP method. Experiment results show that the proposed CP models outperform existing algorithms; in particular, several best‐known solutions of benchmark instances are improved by our CP method.
RETRACTED: A novel method of material demand forecasting for power supply chains in industrial applications
Authors: Xiao Yu , Jun Zhu , Lei Huang , Sharma Ashutosh , Sharma Amit
Published: February 2021

Based on research on big data, data mining and other relevant technical theories, a power material demand analysis system is designed and implemented based on big data technology. The main aim of the study is to forecast material demand and provide data support for decision‐makers. The system includes a data centre subsystem and an application subsystem. At the same time, two kinds of collaborative transmission process models of supply chain information are established, and simulation analysis is carried out on the two models by the Monte Carlo method to verify the effect of collaborative transmission of information flow in supply chains within big data environments. The major contribution of the work is the design of a supply chain model with the help of big data. The impacts of the Internet of Things with empirical studies and limited models are the focuses of the study. It can be seen from the simulation results that there will be a minimum to minimise the cost under the two supply chain information‐transfer process models. The manufacturing cost of the big data platform is about lower than that of the traditional supply chain, and increased delay costs accordingly lead to increased costs for manufacturers in both supply chains.
Industry 4.0 in the logistics field: A bibliometric analysis
Authors: Bigliardi Barbara , Casella Giorgia , Bottani Eleonora
Published: February 2021

Logistics plays an essential role in supply chain management to plan and coordinate the movement of products in a timely, safely and effectively way. The recent term Logistics 4.0 focusses on the specific applications of Industry 4.0 in the area of logistics and was created as an integral part of the Industry 4.0 concept. This study aims to contribute to the state‐of‐the‐art about this topic by analysing and reviewing the scientific literature relating to Industry 4.0 applied to the logistics field. By means of a query on the Scopus database (www.scopus.com), 131 articles were retrieved and judged in line with the research topic. A bibliometric analysis identified the most relevant articles, authors, keywords, countries and journals on this subject. To the best of the authors' knowledge, this is the first systematic review of Logistics 4.0 using bibliometric analysis. Finally, the research gaps identified will provide a reference point that will encourage and guide interested researchers for future study.
Interference coordination and throughput maximisation in an unmanned aerial vehicle‐assisted cellular: User association and three‐dimensional trajectory optimisation
Authors: Yuan Zhichao , Jiang Kaisheng , Jia Weijie , Liu Rongwei , Wang Zhijun , Mao Xinyu
Published: February 2021

Unmanned aerial vehicles in wireless communications have caught great attention in unmanned aerial vehicle assisted communications and cellular‐connected unmanned aerial vehicles. However, the unmanned aerial vehicle's advantage of strong line‐of‐sight channels also brings about severe and extensive interference between unmanned aerial vehicle and the terrestrial communication networks and between multiple unmanned aerial vehicles. This paper jointly optimises the unmanned aerial vehicle's three‐dimensional trajectory and ground users' association schemes with the unmanned aerial vehicle and ground base station to reduce interference. In consideration of fairness, the authors formulate the optimisation problem as maximising the minimum average throughput among all ground users, a mixed‐integer non‐convex problem that is challenging to tackle. To ease the difficulties, the authors have the optimisation problem relaxed and propose a suboptimal solution in the framework of the block successive upper‐bound minimisation algorithm. Furthermore, an improved block successive upper‐bound minimisation based penalty algorithm is obtained to avoid the local maximum point problem. Numerical simulations have validated our schemes.
On the tuning of a nonlinear energy‐based regulator for the positioning of a fully actuated surface marine craft
Authors: Kazantzidou Christina , Perez Tristan , Valentinis Francis , Donaire Alejandro
Published: February 2021

The authors address the problem of tuning a non‐linear energy‐based regulator for the positioning of a surface marine craft. Interconnection and damping assignment passivity‐based control (IDA‐PBC) is used for the control design, resulting in passive target dynamics that can be expressed as a port‐Hamiltonian system (PHS). The IDA‐PBC methodology has been successfully utilised in several applications, however, there has been minimal development in tuning methods that can analytically assist the designer to achieve desired response characteristics. It is demonstrated that eigenvalue assignment of the linearised target dynamics in PHS form can significantly aid the tuning process. Based on this analysis, the authors propose a systematic tuning approach to achieve certain performance and response characteristics. A comprehensive demonstration of the proposed tuning method is provided for the position regulation of an underwater vehicle in the horizontal plane in a case study, where numerical analysis of robustness is also conducted.
An overview of various faults detection methods in synchronous generators
Authors: Mostafaei Mohsen , Faiz Jawad
Published: February 2021

Synchronous generator (SG) plays a vital and critical role in the power system by supplying electric power to consumers. Various faults in SGs can cause some catastrophic events such as power disruption or blackout. These faults can be classified into two electrical and mechanical faults. Short circuit in stator windings and field winding are electrical fault while bearing, static/dynamic eccentricity, and broken damper bars faults are mechanical one. Unlike the induction machines, there are no much researches in SGs condition monitoring owing to its complex behaviour against the faults. Herein, the SG modelling approaches are presented briefly to elaborate shortcoming and challenging issues in the modelling, and then a comprehensive review of various electrical and mechanical fault detection methods is presented.
A flexible virtual inertial control algorithm for ship with propulsion load and pulse load
Authors: Yunfeng Lin , Lijun Fu , Xiongbo Xiao
Published: February 2021

The pulse load of an integrated power system (IPS) ship can produce very high power intermittently in a short period of time. Owing to the limited DC bus capacitance, the periodic pulse load charging and discharging process can make the IPS system state variables have a periodic alternating process during electromagnetic transients, especially at the bus voltage. In order to alleviate this problem, it is necessary to find a suitable control strategy. At first, this article establishes a mathematical model of DC bus voltage dynamics and propulsion motor load. Then, a flexible energy scheduling algorithm is proposed to coordinate the propulsion motor load and the pulse load based on the flexibility of IPS energy scheduling and the concept of virtual inertia. This algorithm can adaptively change the virtual inertia of the DC bus according to the pulse load power level and the propulsion motor load level to mitigate the impact of the pulse load on the IPS system. At the same time, the algorithm is also distributed and has little impact on the propulsion system. Finally, the effectiveness of the algorithm is verified through the mixed simulation of PSCAD and MATLAB and the hardware in the loop test.
Study on the effectiveness of commercial anti‐islanding algorithms in the prospect of mass penetration of PVs in low‐voltage distribution networks
Authors: Boubaris Alexandros , Kyritsis Anastasios , Babouras Konstantinos , Frantzeskakis Syllas , Papanikolaou Nick , Papadopoulos Theofilos , Vidaurrazaga Iñigo , Alonso Ricardo
Published: February 2021

In the coming years, distribution grids will be progressively flooded by renewable energy sources (RES) that will be interconnected with the main grid through power electronic converters. Photovoltaics (PVs) are one of the most promising renewable technologies even for densely built‐up areas where space problems are inevitable. The high penetration prospect of PV facilities on low‐voltage distribution networks raises questions regarding the necessity of advanced functions that will enable electronically coupled RES to support the operation of distribution grids and to enhance their reliability. In this context, the objective of this study is to investigate the effectiveness of various islanding prevention measures installed in commercial PV inverters, when multiple inverters are operating in parallel with a low‐voltage distribution network (LVDN). Extensive experiments were performed under various PV penetration levels, linear/non‐linear load and over/under voltage and over/under frequency conditions, as well as for various values of total harmonic distortion of the mains voltage. Further to the primary statistical analysis, the results were analysed in depth by advanced mathematical methods such as box plot and cluster analysis. The findings of this study indicate that commercial anti‐islanding techniques present a high probability of failure in the case of multiple PV units at the same point of common coupling, calling for new and more advanced algorithms.
Optimal day‐ahead scheduling of multiple integrated energy systems considering integrated demand response, cooperative game and virtual energy storage
Authors: Chen Changming , Deng Xin , Zhang Zhi , Liu Shengyuan , Waseem Muhammad , Dan Yangqing , Lan Zhou , Lin Zhenzhi , Yang Li , Ding Yi
Published: February 2021

As the physical carrier of the Energy Internet, integrated energy system (IES) is a future development trend in the energy field, and the optimal scheduling of IES for improving energy utilisation efficiency has become a hot topic. An optimal day‐ahead scheduling model of multiple IESs considering integrated demand response (IDR), cooperative game and virtual energy storage (VES) is proposed innovatively in this study to maximise the overall benefits of the cooperative alliance. IDR and VES are considered together for the first time to optimise the internal scheduling of each IES, where IDR can enhance the response potential on the demand side and VES can improve the scheduling flexibility of IES. Cooperative game theory is utilised to process the energy trading mechanism among multiple IESs and the Nash bargaining method is utilised to solve the cooperative game problem and obtain a fair and Pareto‐optimal energy trading strategy. The case study shows that the proposed model effectively improves the operating benefits and the renewable energy penetration levels of each IES.
Surrogate‐assisted optimal re‐dispatch control for risk‐aware regulation of dynamic total transfer capability
Authors: Qiu Gao , Liu Youbo , Liu Junyong , Wang Lingfeng , Liu Tingjian , Gao Hongjun , Jawad Shafqat
Published: February 2021

To enable reliable power delivery through transmission tie‐lines, total transfer capability (TTC) must be calculated and regulated to accommodate the transferred amount. However, the traditional optimal power flow (OPF)‐based total transfer capability calculation is computationally expensive for efficient total transfer capability control due to the inclusion of a large set of differential‐algebraic equations (DAEs) to verify transient stability constraints. In order to enable practicable total transfer capability regulation, a novel risk‐aware deep learning‐assisted paradigm is proposed here. First, a deep belief network (DBN) is employed to establish the total transfer capability predictor and surrogate the computation‐intensive differential‐algebraic equations in original optimal power flow formulas, simplifying the high‐dimensional and intractable constraints deep belief networks without loss of nonlinearity. Particularly, in order to be aware of control risk from the predictive error of the deep belief networks, prediction intervals (PIs) are produced improved by using ensemble learning and used to disclose the probability of insufficient actions, further guaranteeing the sufficient and cost‐effective control by compromising the tradeoff between cost and risk. Symbiotic organisms search (SOS) is then applied to solve the proposed risk‐aware deep belief network‐assisted total transfer capability control problem globally. The numerical studies testify that the proposed method enables economical, reliable, and full nonlinearity‐retained dynamic total transfer capability regulation control within a risk‐free surrogate‐assisted and tractable physical model‐driven hybrid framework.
An efficient and layout‐independent automatic license plate recognition system based on the YOLO detector
Authors: Laroca Rayson , Zanlorensi Luiz A. , Gonçalves Gabriel R. , Todt Eduardo , Schwartz William Robson , Menotti David
Published: February 2021

This paper presents an efficient and layout‐independent Automatic License Plate Recognition (ALPR) system based on the state‐of‐the‐art you only look once (YOLO) object detector that contains a unified approach for license plate (LP) detection and layout classification to improve the recognition results using post‐processing rules. The system is conceived by evaluating and optimizing different models, aiming at achieving the best speed/accuracy trade‐off at each stage. The networks are trained using images from several datasets, with the addition of various data augmentation techniques, so that they are robust under different conditions. The proposed system achieved an average end‐to‐end recognition rate of 96.9% across eight public datasets (from five different regions) used in the experiments, outperforming both previous works and commercial systems in the ChineseLP, OpenALPR‐EU, SSIG‐SegPlate and UFPR‐ALPR datasets. In the other datasets, the proposed approach achieved competitive results to those attained by the baselines. The authors' system also achieved impressive frames per second (FPS) rates on a high‐end GPU, being able to perform in real time even when there are four vehicles in the scene. An additional contribution is that the authors manually labelled 38,351 bounding boxes on 6,239 images from public datasets and made the annotations publicly available to the research community.
Enhanced electromechanical performance through chemistry graft copper phthalocyanine to siloxane‐modified polyurethane and interpenetrate with siloxane silicon rubber as composite actuator material
Authors: Huang Tingting , Yuan Bolei , Tang Jun , Zhang Yunhe
Published: February 2021

Researchers are devoted to developing dielectric elastomers (DEs) with excellent electromechanical properties as an artificial muscle material. The authors report a new class of semi‐interpenetrating network (semi‐IPN) composites that contains siloxane‐modified linear polyurethane (PU) and silicone rubber through reasonable design of polymer structure. The organic‐filler copper phthalocyanine (CuPc) is chemically grafted into the semi‐interpenetrating network as a cross‐linking point and exhibits excellent dispersibility in the matrix. The various properties of the obtained composite films are also evaluated. The dielectric constant (8.65 at 1 kHz) and maximum actuation strain at 30 MV m−1 (5.32%) are significantly higher than those of semi‐IPN composites.
Electromagnetic interference‐based comparative study between transformerless H5 and optimised H5 grid‐connected photovoltaic inverters
Authors: Kraiem Sana , Hamouda Mahmoud , Ben Hadj Slama Jaleleddine
Published: February 2021

In this study, a comparative study between two single‐phase transformerless grid‐connected photovoltaic (PV) inverters, namely H5 and optimised H5 (oH5), is carried out based on conducted electromagnetic interference (EMI) performance. For this purpose, a high‐frequency (HF) model of the grid‐connected inverters is proposed and simulated using Simulation Program with Integrated Circuit Emphasis (SPICE)‐based circuit simulation software. Moreover, an experimental setup is developed to measure the conducted emissions. The obtained results show an EMI advantage of the oH5 inverter at low frequencies but not at HF frequencies. Therefore, a mitigation method is proposed to optimise the oH5 topology in the HF range. It consists in using only one Resistor–Capacitor (RC) snubber circuit connected in parallel with the inverter's extra switch. The obtained results show that the oH5 inverter with only one RC snubber circuit provides lower conducted EMI than the H5 in a wider frequency range without worsening the efficiency. The proposed EMI mitigation method can therefore be considered as an adequate and preferred solution for the transformerless grid‐connected oH5 PV inverter.
xCOLD GASS and xGASS: Radial metallicity gradients and global properties on the star-forming main sequence
Authors: Lutz K. A. , Saintonge A. , Catinella B. , Cortese L. , Eisenhauer F. , Kramer C. , Moran S. M. , Tacconi L. J. , Vollmer B. , Wang J.
Published: February 2021

Context. The xGASS and xCOLD GASS surveys have measured the atomic (H I) and molecular gas (H2) content of a large and representative sample of nearby galaxies (redshift range of 0.01 < z < 0.05).

Methods. We present optical longslit spectra for a subset of the xGASS and xCOLD GASS galaxies to investigate the correlation between radial metallicity profiles and cold gas content. In addition to previous data, this paper presents new optical spectra for 27 galaxies in the stellar mass range of 9.0 ≤ log M⋆ [M⊙] ≤10.0.

Methods. The longslit spectra were taken along the major axis of the galaxies, allowing us to obtain radial profiles of the gas-phase oxygen abundance (12 + log(O/H)). The slope of a linear fit to these radial profiles is defined as the metallicity gradient. We investigated correlations between these gradients and global galaxy properties, such as star formation activity and gas content. In addition, we examined the correlation of local metallicity measurements and the global H I mass fraction.

Results. We obtained two main results: (i) the local metallicity is correlated with the global H I mass fraction, which is in good agreement with previous results. A simple toy model suggests that this correlation points towards a ‘local gas regulator model’; (ii) the primary driver of metallicity gradients appears to be stellar mass surface density (as a proxy for morphology).

Conclusions. This work comprises one of the few systematic observational studies of the influence of the cold gas on the chemical evolution of star-forming galaxies, as considered via metallicity gradients and local measurements of the gas-phase oxygen abundance. Our results suggest that local density and local H I mass fraction are drivers of chemical evolution and the gas-phase metallicity.
The 800 pc long tidal tails of the Hyades star cluster
Authors: Jerabkova Tereza , Boffin Henri M. J. , Beccari Giacomo , de Marchi Guido , de Bruijne Jos H. J. , Prusti Timo
Published: February 2021

The tidal tails of stellar clusters provide an important tool for studying the birth conditions of the clusters and their evolution, coupling, and interaction with the Galactic potential. The Gaia satellite, with its high-quality astrometric data, opened this field of study, allowing us to observe large-scale tidal tails. Theoretical models of tidal-tail formation and evolution are available. However, the exact appearance of tidal features as seen in the Gaia catalogue has not yet been studied. Here we present the N-body evolution of a Hyades-like stellar cluster with backward-integrated initial conditions on a realistic 3D orbit in the Milky Way galaxy computed within the AMUSE framework. For the first time, we explore the effect of the initial cluster rotation and the presence of lumps in the Galactic potential on the formation and evolution of tidal tails. For all of our simulations we present Gaia observables and derived parameters in the convergent point (CP) diagram. We show that the tidal tails are not naturally clustered in any coordinate system and that they can span up to 40 km s−1 relative to the cluster centre in proper motions for a cluster age of 600–700 Myr. Models with initial rotation result in significant differences in the cluster mass loss and follow different angular momentum time evolution. Thus the orientation of the tidal tails relative to the motion vector of the cluster and the current cluster angular momentum constrain the initial rotation of the cluster. We highlight the use of the standard CP method in searches for co-moving groups and introduce a new compact CP (CCP) method that accounts for internal kinematics based on an assumed model. Using the CCP method, we are able to recover candidate members of the Hyades tidal tails in the Gaia Data Release 2 and early Data Release 3 (eDR3) reaching a total extent of almost 1 kpc. We confirm the previously noted asymmetry in the detected tidal tails. In the eDR3 data we recovered spatial overdensities in the leading and trailing tails that are kinematically consistent with being epicyclic overdensities and thus would present candidates for the first such detection in an open star cluster. We show that the epicyclic overdensities are able to provide constraints not only on the cluster properties, but also on the Galactic potential. Finally, based on N-body simulations, a close encounter with a massive Galactic lump can explain the observed asymmetry in the tidal tails of the Hyades.
Multi-instrumental view of magnetic fields and activity of ϵ Eridani with SPIRou, NARVAL, and TESS
Authors: Petit P. , Folsom C. P. , Donati J.-F. , Yu L. , do Nascimento J.-D. , Jeffers S. V. , Marsden S. C. , Morin J. , Vidotto A. A.
Published: February 2021

Aims. We report on observations of the active K2 dwarf ϵ Eridani based on contemporaneous SPIRou, NARVAL and TESS data obtained over two months in late 2018, when the activity of the star was reported to be in a non-cyclic phase.

Methods. Near-infrared (NIR) spectropolarimetry was obtained using SPIRou over four nights in late September, while visible spectropolarimetry was collected with NARVAL over 20 nights, spread between 18 September and 07 November. We first recovered the fundamental parameters of the target from both visible and NIR spectral fitting. The large-scale magnetic field was investigated from polarimetric data. From unpolarized spectra, we estimated the total magnetic flux through Zeeman broadening of magnetically sensitive NIR lines and the chromospheric emission using the CaII H&K lines. The photometric monitoring, secured with TESS between 19 October and 15 November, is modelled with pseudo-periodic Gaussian process regression.

Results. Fundamental parameters of ϵ Eridani derived from visible and NIR wavelengths provide us with consistent results, which also agree with published values. We report a progressive increase of macroturbulence towards larger NIR wavelengths. Zeeman broadening of individual lines highlights an unsigned surface magnetic field Bmono = 1.90 ± 0.13 kG, with a filling factor f = 12.5 ± 1.7% (unsigned magnetic flux Bf = 237 ± 36 G). The large-scale magnetic field geometry, chromospheric emission and broadband photometry display clear signs of non-rotational evolution over the course of data collection. Characteristic decay times deduced from the light curve and longitudinal field fall in the range 30–40 days, while the characteristic timescale of surface differential rotation, as derived through the evolution of the magnetic geometry, is equal to 57 ± 5 days. The large-scale magnetic field exhibits a combination of properties not observed previously for ϵ Eridani, with a surface field among the weakest previously reported, but this field is also mostly axisymmetric, and is dominated by a toroidal component.
DESIGN OPTIMIZATION OF THE HOLOS-QUAD MICRO-REACTOR CONCEPT
Authors: Stauff N. E. , Lee C. H. , Wells A. , Filippone C.
Published: February 2021

The Holos-Quad micro-reactor concept is proposed by HolosGen LLC to generate 22 MWt with a lifetime of approximately 8 effective full power years (EFPYs) for civilian applications. The design is based on a very innovative high-temperature gas-cooled reactor concept using four Subcritical Power Modules (SPMs) that fit into one commercial 40-foot transport ISO container. A rigorous design approach was employed in order to ensure that all input parameters were fully investigated and the best solutions possible were considered. The first step of this approach consisted of properly defining the Holos-Quad design problem by identifying the design objectives, the operational constraints, and the input parameters. In the second step, a sensitivity analysis was performed to enable a preliminary investigation of the input parameters to identify the correlations among input and output variables. Finally, the design optimization was performed in the third step, employing a genetic algorithm to effectively explore the highly constrained input parameters and find global optimal solutions. The multi-objective optimization identified various core solutions that would be optimum solutions for different types of applications. For applications where economics matters less and the ease of transportation matters more, a core weight of ~15 tons could achieve a lifetime of ~3.5 EFPYs. For applications where economics matters more and the ease of transportation matters less, a lifetime of 8.3 EFPYs could be achieved with a total core weight of ~26.7 tons.
INFLUENCE OF FUEL FLOW RATE VARIATION ON MOLTEN SALT REACTOR PERFORMANCE
Authors: Negri O , Abram T
Published: February 2021

Molten Salt Reactors are Gen-IV reactors that use liquid fuel. Fluid fuel allows continuous removal of fission gases as well as batch fuel reprocessing. With these control mechanisms the system can be sustained within the desired operating temperature range and required power output. These methods rely on the presence of a chemical processing plant on-site that adds complexity. This also creates a risk of processing plant unavailability due to faults, emergency downtime or maintenance. The work considers variation of fuel salt flow rate in Molten Salt Reactors as a means of controlling reactor operation without using reprocessing. The analysis is performed using the Molten Salt Fast Reactor as an example. An extended version of the SERPENT Monte-Carlo transport code coupled with OpenFOAM generic platform were used for capturing delayed neutron drift, decay heat, gaseous fission product removal, calculating fuel salt velocity vectors and the fuel temperature distribution. The two models were coupled via a script that accounted for reactivity insertion between time steps and the changes caused in the fission power. Results confirm that, while operating at constant power, the difference between fuel inlet and outlet temperatures increase as the flow rate decreases. Burnup analysis has shown that while the average fuel temperature continues to reduce with time, the difference between inlet and outlet temperatures can be controlled by varying the flow rate while maintaining constant power. Finally, the variation in the fuel flow rate has been shown to extend the reactor operating time with no insertion of additional fissile inventory.
ADAPTIVE SOLUTION OF THE NEUTRON DIFFUSION EQUATION WITH HETEROGENEOUS COEFFICIENTS USING THE MIXED FINITE ELEMENT METHOD ON STRUCTURED MESHES
Authors: Do Minh-Hieu , Ciarlet Patrick , Madiot François
Published: February 2021

The neutron transport equation can be used to model the physics of the nuclear reactor core. Its solution depends on several variables and requires a lot of high precision computations. One can simplify this model to obtain the SPN equation for a generalized eigenvalue problem. In order to solve this eigenvalue problem, we usually use the inverse power iteration by solving a source problem at each iteration. Classically, this problem can be recast in a mixed variational form, and then discretized by using the Raviart-Thomas-Nédélec Finite Element. In this article, we focus on the steady-state diffusion equation with heterogeneous coefficients discretized on Cartesian meshes. In this situation, it is expected that the solution has low regularity. Therefore, it is necessary to refine at the singular regions to get better accuracy. The Adaptive Mesh Refinement (AMR) is one of the most effective ways to do that and to improve the computational time. The main ingredient for the refinement techniques is the use of a posteriori error estimates, which gives a rigorous upper bound of the error between the exact and numerical solution. This indicator allows to refine the mesh in the regions where the error is large. In this work, some mesh refinement strategies are proposed on the Cartesian mesh for the source problem. Moreover, we numerically investigate an algorithm which combines the AMR process with the inverse power iteration to handle the generalized eigenvalue problem.
COUPLING OF nTRACER TO COBRA-TF FOR HIGH-FIDELITY ANALYSIS OF VVERs
Authors: Papadionysiou Marianna , Seongchan Kim , Hursin Mathieu , Vasiliev Alexander , Ferroukhi Hakim , Pautz Andreas , Han Gyu Joo
Published: February 2021

Paul Scherrer Institut is developing a high-resolution multi-physics core solver for VVER analysis. This work presents the preliminary stages of the development, specifically the coupling of the 3D pin-by-pin neutronic solver nTRACER to the sub-channel thermal-hydraulic code COBRA-TF for single assembly multi-physics steady state calculations. The coupling scheme and the modifications performed in the codes are described in details. The results of the coupled nTRACER/COBRA-TF calculations are compared to the ones of a standalone nTRACER calculation where the feedbacks are provided by a simplified 1D thermal-hydraulic solver. The agreement is very good with fuel temperature differences around 10 K which can be attributed to the different correlations used in the various solvers. The cross-comparison of the two multi-physics computational routes serves as a preliminary verification of the coupling scheme developed between nTRACER and COBRA-TF.
A 3-D FINITE ELEMENT FEW-GROUP DIFFUSION CODE AND ITS APPLICATION TO GENERATION IV REACTOR CONCEPTS
Authors: Seubert A.
Published: February 2021

In this paper, a recently developed 3-d few-group finite element-based diffusion code is de-scribed. Its geometrical flexibility allows future modeling of complex and irregular geometries of (very) small and medium size reactor concepts –(v)SMRs –being in the spotlight for energy provision in remote residential and industrial regions or for space applications, and also liquid metal cooled Generation IV reactors where thermally induced core deformation results in localized assembly lattice distortions which cannot be treated by traditional 3-d neutron kinetics codes devoted to the regular lattices of LWR and Generation IV systems. The description of the implemented FEM solution method is followed by first applications to a prismatic (or block type) high-temperature reactor MHTGR-350MW within an OECD/NEA benchmark activity and to the sodium cooled fast reactor concept ASTRID within the past EU project ESNII+. Finally, an outlook to planned further code development activities is given.
ASSESSMENT OF PARALLEL SIMULATED ANNEALING PERFORMANCE WITH THE NEXUS/ANC9 CORE DESIGN CODE SYSTEM
Authors: Ivanov Boyan D. , Kropaczek David J.
Published: February 2021

The method of parallel simulated annealing is being considered as a loading pattern optimization method to be used within the framework of the latest Westinghouse core design code system NEXUS/ANC9. A prototype version of NEXUS/ANC9 that incorporates the parallel simulated annealing method was developed. The prototype version was evaluated in terms of robustness, performance and results. The prototype code was used to optimize LPs for several plants and cycles, including 2-loop, 3-loop and 4-loop Westinghouse plants. Different fuel assembly lattices with IFBA, WABA and Gadolinium burnable absorbers were also exercised in these cores. Different strategies were evaluated using different options in the code. Special attention was paid to the robustness and performance when different number of parallel processes were used with different size of Markov chain.
EFFECTS OF FUEL TEMPERATURE-SHAPING FUNCTIONS ON XENON OSCILLATIONS
Authors: Walker Erik , Godfrey Andrew , Stimpson Shane , Collins Benjamin
Published: February 2021

In coupled multiphysics simulations, single pin-averaged values are typically used to describe the temperature, power, and burnup within a given fuel pin. However, since xenon oscillations are largely driven by fuel temperatures, radially dependent quantities have been implemented in the Virtual Environment for Reactor Applications. These radial-shaping functions are based on Zernike polynomial expansions and allow information to pass effectively between codes with differing spatial meshes. This work examines the effects of radial fuel temperature-shaping functions on the behavior of axial xenon oscillations.

A test problem was developed from full-core, multi-cycle depletions using as-built fuel data. The center 25 assemblies of the full-core case were used to test the radial-shaping function by inducing an axial xenon oscillation using an instantaneous control rod movement. The test case was run with and without the radial shapes, and each component was also run individually. Including the shaping functions significantly impacted the xenon oscillations for this problem; the magnitude and period of the oscillations were altered, and large pin power and soluble boron differences were observed. Testing each component individually showed that the radial fuel temperature-shaping function had the largest effect.
AN IMPROVED ENERGY DEPOSITION MODEL IN MPACT AND EXPLICIT HEAT GENERATION COUPLING WITH CTF
Authors: Liu Yuxuan , Salko Robert , Kim Kang Seog , Wang Xinyan , Kabelitz Matthew , Kochunas Brendan , Collins Benjamin , Martin William
Published: February 2021

The default energy deposition model in the CASL neutronics code MPACT assumes all fission energy is deposited locally in fuel rods. Furthermore, equilibrium delayed energy release is assumed for both steady-state and transient calculations. These approximations limit the accurate representation of the heat generation distribution in space and its variations over time, which are essential for power distribution and thermal-hydraulic coupling calculations. In this paper, an improved energy deposition model is presented in both the spatial and time domains. Spatially, the energy deposition through fission, neutron capture, and slowing-down reactions are explicitly modeled to account for the heat generation from all regions of a reactor core, and a gamma smearing scheme is developed that utilizes the gamma sources from neutron fission and capture. In the time domain, the delayed energy release is modeled by solving an additional equation of delayed heat emitters, similar to the equation of delayed neutron precursors. To allow the explicit heat generation coupling, the interfaces between MPACT and CTF were updated to transfer separate heat sources for different material regions (fuel, clad, moderator and guide tube). The results show that the distributions of the energy deposition between MPACT and MCNP agree very well for various 2-D assembly and quarter-core problems without TH feedback. The MPACT/CTF coupled calculation for the hot full power quarter-core case exhibited a reduced peak pin power by 2.3% and a reduced peak fuel centerline temperature by 17 K when using the explicit energy deposition and heat transfer. The new model also shows a maximum 100 pcm keffeffect on assembly depletion problems and an increased overall energy release by 7% in a PWR reactivity-initiated accident (RIA) problem.