bluuebunny/crossref_metadata_2025 huggingface dataset:
Sequence‐based centrality measures in maritime transportation networks
Authors: Li Jing , Wang Xuantong , Zhang Tong
Published: February 2021

Performing centrality analysis on nodes from transportation networks are critical to identify important hubs, understand travel decisions, and assess system performances. Current centrality measures are based on topological characteristics of nodes and edges. When applying those measures to large‐scale transportation networks, two problems remain unsolved. First, measures are computed based on simplified travel paths, which only include origins and destinations. Due to the lack of information about waypoints of routes, such network representation may not preserve fine level information about waypoints, routes, and traffic flow patterns, resulting in an inaccurate view of centrality. Second, most centrality measures are global measures that rank all nodes in a network, thus failing to detect nodes of regional importance. Therefore, this paper describes an approach that leverages the concept of sequences to identify key waypoints from frequent travel paths and detect community structures of transportation networks. This approach extends two complementary centrality measures to define the role of nodes within communities. The approach has been tested using tracking data of ships in a regional maritime transportation network. Compared to traditional measurement approaches, the proposed approach can construct compact communities, discover prominent waypoints, and add new insight with local centrality measure.
Short‐term traffic congestion prediction with Conv–BiLSTM considering spatio‐temporal features
Authors: Li Tao , Ni Anning , Zhang Chunqin , Xiao Guangnian , Gao Linjie
Published: February 2021

For many intelligent transportation applications, traffic congestion prediction is quite essential. If traffic congestion on the road ahead can be accurately and promptly predicted, and routes can be planned reasonably based on the prediction results, traffic congestion can be effectively alleviated. Aiming at the spatio‐temporal correlation and evolution characteristics of traffic flow data, the Conv–BiLSTM module comprising a convolutional neural network (CNN) and a bidirectional long short‐term memory (BiLSTM) is proposed, considering the spatio‐temporal features. Firstly, the obtained traffic speed data is folded according to spatio‐temporal features, and a three‐dimensional matrix is constructed as the input of the prediction network module. After the spatial features are extracted by the CNN, the temporal features and alignment features are extracted by the BiLSTM, followed by which the prediction results are obtained as an output. Prediction and evaluation experiments on the traffic data of the highway in Shanghai prove that the traffic congestion state predicted by this method is largely consistent with the actual state. The results demonstrate that the proposed method has a higher prediction accuracy compared with the conventional and state‐of‐the‐art methods and is an efficient method of traffic congestion prediction.
Modified deterministic Jaya (DM‐Jaya)‐based MPPT algorithm under partially shaded conditions for PV system
Authors: Deboucha Houssam , Mekhilef Saad , Belaid Sofia , Guichi Amar
Published: February 2021

The output power characteristic of the photovoltaic (PV) panel under partial shading condition (PSC) exhibits multiple peaks: a single global maximum peak (GMP) and several local maximum peaks, which adds more complexity to the maximum power point tracking (MPPT) system. Here, a deterministic modified Jaya (DM‐Jaya)‐based algorithm is proposed for tracking the GMP, where the updating solution formula and the step size in the vicinity of the GMP of the generic Jaya algorithm have been significantly improved, these improvements provide many pros, including quick convergence time, one parameter needs to be tuned, null oscillation in steady‐state, and easily implemented in a low‐cost microcontroller. The proposed DM‐Jaya algorithm is implemented in the hardware prototype; in addition, it is compared to other state‐of‐the‐art techniques under different PSC patterns. The obtained results revealed the effectiveness of the DM‐Jaya and its overall superiority compared to other methods in terms of efficiency and tracking time.
Integration of power‐to‐gas and low‐carbon road transport in Great Britain's future energy system
Authors: Fu Peng , Pudjianto Danny , Strbac Goran
Published: February 2021

Integrating decarbonisation strategies for road transport and electricity is vital to minimise the overall cost of meeting the carbon target. This integration maximises the synergy across different energy sectors to improve the value and utilisation of investment, especially in low‐carbon technologies across all sectors. This study presents an integrated multi‐energy optimisation model to evaluate the economic performance and system implications of different road‐transport decarbonisation strategies and analyse the synergy with the power sector decarbonisation. The large‐scale optimisation model is formulated to consider the interactions across electricity, hydrogen, and transport sectors and used to determine the optimal solutions for investment and sector‐coupling operation in the system. The proposed model is tested using a range of transport decarbonisation scenarios considering the deployment of electric or hydrogen vehicles or their combination and the integration with the power system. The studies analyse the economic performance and optimal energy system portfolios across different scenarios. The results demonstrate the importance of road‐transport and power‐to‐gas integration in Great Britain's future energy system.
Evaluation of data‐driven performance measures for comparing and ranking traffic bottlenecks
Authors: Hale David , Chrysikopoulos Georgios , Kondyli Alexandra , Ghiasi Amir
Published: February 2021

Traffic analysis procedures are becoming more robust over time. However, there is still significant room for improvement both in practitioners’ adoption of robust methods and in robustness of the methods themselves. One example of oversimplified practice involves peak hour or 30th highest hour analysis, which fails to capture the impacts of varying demands and operating conditions. To address this limitation, detailed reliability modelling procedures were developed for the Highway Capacity Manual (HCM), but these procedures bring challenging input data and calibration requirements. A new generation of data‐driven tools is capable of real‐time congestion identification, but their performance measures are only beginning to improve and evolve. Finally, comparing and ranking congested locations (i.e. bottlenecks) on the basis of experience and judgment lacks credibility unless backed by quantitative results. This study discusses the development of new and innovative performance measures for congestion measurement. A case study of ranking eight real‐world bottlenecks based on the proposed measures and existing HCM measures produced new insights that could improve both approaches. Ideally, these new insights and methods would be accepted by agencies and/or commercial products for a new level of robustness in congestion measurement.
One‐step hydrothermal synthesis of double core‐shell oxygen‐incorporated molybdenum disulfide and its tribological properties
Authors: Chen Ying , Li Yuan , Liang Yuning , Chen Xuesong , Cui Jinjin
Published: February 2021

Using a simple one‐step hydrothermal method, benzyl triethylammonium chloride was used to assist the synthesis of double core‐shell oxygen‐incorporated molybdenum disulfide (DB‐O‐MoS2), and its friction and wear properties were measured on the MRS‐10A four‐ball testing machine. They were characterised by X‐ray diffraction, scanning electron microscope, transmission electron microscope, thermogravimetry, Brunner−Emmet−Teller and Fourier transform infrared spectroscope. Friction and wear properties of DB‐O‐MoS2 were measured at different concentrations. The results showed that the tribological properties of SN 5W‐40 base oil have been improved by adding the DB‐O‐MoS2 as lubricant additives. The possibility of DB‐O‐MoS2 mechanisms by which the nanolubricants improved the tribological properties were put forward. Therefore, research on DB‐O‐MoS2 is beneficial to the development of new engine lubricant additives.
Comment on ‘ElGamal cryptosystem‐based secure authentication system for cloud‐based IoT applications’
Authors: Irshad Azeem , Chaudhry Shehzad Ashraf
Published: February 2021

This comment is presented to identify the drawbacks in a recently demonstrated scheme by Maitra et al., SAS‐Cloud: doi:10.1049/iet-net.2019.0004, which adopted an ElGamal cryptosystem‐based technique for biometric authentication in cloud‐based IoT applications. In this protocol, the authors claim that their scheme provides mutual authentication. However, it is demonstrated in this article that the protocol merely supports unilateral authentication, which may result in clogging attack on the server's end. This is because the latter is unable to verify the authentication request in absolute terms, which might lead to resource clogging as well as denial of service attack affecting its Quality of Service (QoS).
The eddy current loss segmentation model of permanent magnet for temperature analysis in high‐speed permanent magnet motor
Authors: Zhang Meiwei , Luo Shifan , Liu Xiaoke , Li Weili
Published: February 2021

The rotor eddy current loss of high‐speed permanent magnet motor has an important influence on the temperature distribution of permanent magnet. In traditional method, the unbalanced distribution of eddy current in permanent magnet is ignored, and the eddy current loss is applied to the calculation of temperature field in the form of average heat density, which makes a certain error in the calculation of the temperature field in permanent magnet motors. This study proposes the 50 kW and 30,000 rpm high‐speed permanent magnet prototype and an eddy current loss segmentation model of permanent magnet. The unbalanced distribution of eddy current in permanent magnet is considered in this model, and the permanent magnet is divided into different regions. According to the eddy current loss segmentation model, the eddy current losses in different regions are obtained, then the heat density in different regions of permanent magnet is applied to the calculation of temperature field in the motor. The application of the proposed model is simple and convenient, and makes temperature simulation results closer to the actual situation. At the same time, in order to verify the accuracy of the model, the temperature calculation results using the proposed model are compared with the traditional method, and both the results are verified by relevant experiments.
Improved dynamic voltage restorer with reduced capacity of power inverter and energy storage for voltage sag mitigation
Authors: Guo Qi , Tu Chunming , Jiang Fei , Zhu Rongwu , Xiao Fan , Chen Cheng
Published: February 2021

As one of the most representative series active compensators, dynamic voltage restorer (DVR) can solve voltage‐related power quality uses effectively. The in‐phase voltage control and energy‐optimised control are the two typical control strategies of DVR. However, the in‐phase voltage control results in a large amount of active power exchange between the main grid and the dc link of DVR, and hence high capacity of storage system is needed in the dc link while the energy‐optimised strategy requires high injected voltage, resulting in oversizing of the DVR inverter. Thus, in order to avoid the aforementioned drawbacks, this study proposes a modified DVR, which connects an external capacitor in series with the LC filter (LCC) of DVR (LCC‐DVR). Based on the operational principles of the LCC‐DVR, an updated procedure of reference voltage is proposed to avoid overmodulation of DVR caused by load variations, ensuring the continuous operation capability of the LCC‐DVR. The overall control scheme of the LCC‐DVR and the comparative analysis among the proposed strategy and traditional strategies are also presented. The effectiveness of the proposed topology and method is clearly validated by the simulation and experimental results.
Seamless control for single‐phase high gain quasi‐switched impedance source multilevel inverter for distributed generation application
Authors: Thummalagunta Ajaykumar , Patne Nita R. , N Kodandaram
Published: February 2021

The single‐stage buck‐boost multilevel inverters are getting more attention even in low‐voltage and low power distributed generation applications due to high reliability with shoot‐through invulnerability. But the inherent boosting ability of most of the inventions is constrained by the device stresses and deprived performance at a low modulation index. In this study, a new hybrid quasi‐switched boost circuit is integrated with a reduced switch single‐phase multilevel inverter to accomplish a high gain single‐stage conversion at low device stress and high modulation index. It can be extended to a multi‐cell configuration for further enhancement of gain. Also, a control scheme is presented to achieve enhanced performance during standalone and grid‐connected modes. This scheme assists the need of providing reliable electrical supply to the critical local loads along with serving power to the main grid. It also provides islanding with a seamless transition for the period of grid failure. The proposed inverter's features, robustness, and flexibility of the control under both input voltage and output power disturbances make it more suitable for residential rooftop PV generation. A 500 W laboratory prototype is built for experimental verification. Both simulation and experimental studies validate the proposed theory.
Solar‐powered switched reluctance motor‐driven water pumping system with battery support
Authors: Mishra Anjanee Kumar , Singh Bhim
Published: February 2021

This work deals with the development of an efficient and reliable solar photovoltaic‐fed water pump with a battery energy storage (BES). This system ensures a continuous and rated supply of water in all working conditions. A new control logic for BES is developed, which significantly improves the overall response of the system. The support of the battery as a backup source is obtained through a bidirectional DC‐DC converter. Both the charging/discharging control and maximum power tracking of the solar panel are achieved through this bidirectional converter, whereas the voltage asymmetry compensation across split capacitors at DC link and motor drive controls are supervised by switched reluctance motor converter. The performance of the present scheme is examined through both simulated and experimental responses and is found adequate under all operational scenarios.
Optimal day‐ahead scheduling for active distribution network based on improved information gap decision theory
Authors: Ge Xiaolin , Zhu Xiaohe , Ju Xing , Fu Yang , Lo Kwok Lun , Mi Yang
Published: February 2021

In this study, information gap decision theory (IGDT) is reformed to formulate the uncertain parameters of wind power, photovoltaic and load. Traditional IGDT presumes that positive and negative deviations of uncertain parameters of the predicted value are equal, and it would result in imprecise assessment of fluctuated intervals. This study proposes an improved IGDT to overcome the inaccuracy of traditional IGDT by considering unsymmetrical fluctuation levels of uncertainties. For the operation and control of active distribution network, the non‐linear power flow constraints are included and linearised with a novel method based on circumscribed polyhedron approximation, which guarantees the accuracy of the solution results and takes less computing time. Additionally, from the mathematical point of view, the model established in this study is a multilevel optimisation problem, and linear Karush–Kuhn–Tucker conditions are formulated to transform the multilevel optimisation problem into a single‐level optimisation problem. Finally, the economic viability and model applicability are verified through the modified IEEE 33‐node distribution system.
Numerical investigation of inter‐blade cavitation vortex for a Francis turbine at part load conditions
Authors: Sun Longgang , Guo Pengcheng , Luo Xingqi
Published: February 2021

Inter‐blade cavitation vortex at part load has raised significant concerns about operation stability for Francis turbines due to tremendous development and integration of renewable energy resources into power grid. The principal objective of this study is to investigate the flow characteristics of inter‐blade cavitation vortex and its influence on pressure fluctuations for a low‐head Francis model turbine. Unsteady numerical simulations are carried out using shear stress transport turbulence model and Zwart cavitation model. Numerical results yield to a good validation with the experimental data. The findings show that inter‐blade cavitation vortices highlighted by cavitation structure and vortex structure are extremely different at the points adjacent to the incipient line of inter‐blade cavitation vortex. The location of inter‐blade cavitation vortex development in the runner is more sensitive to rotating speed than that to guide vane opening. The formation mechanism of inter‐blade cavitation vortex is attributed to flow separation in the vicinity of the runner hub. Pressure fluctuations induced by inter‐blade cavitation vortex are directly associated with the evolution of vapour volume in the runner and feature wide‐band and low‐frequency characteristic, and the fluctuations on the suction side of the runner blade are significantly magnified because of the presence of inter‐blade cavitation vortex.
An efficient and accurate Mixed‐integer linear programming model for long‐term operations of large‐scale hydropower systems
Authors: Zhao Zhipeng , Cheng ChunTian , Yan Lingzhi
Published: February 2021

Mixed‐integer linear programming is widely used in hydropower reservoirs operation optimisation because of its modelling flexibility, solution stability, and global search capability. A major obstacle to applying mixed‐integer linear programming to hydropower reservoirs operation optimisation, especially for long‐term operations of large‐scale hydropower systems, is the non‐linear phenomenon while converting water energy into electricity, which is normally expressed as a non‐linear bivariate function, that is, hydropower production function. To cross this technological barrier, a novel linearisation method for hydropower production function is proposed. The method uses rectangular meshing techniques to approximate hydropower production function. Then Special Ordered Sets of type 2 (SOS2)constraints are adopted for sub‐rectangle selection, which are formulated based on the binary branching schemes generated by binary reflected grey code. The proposed method can linearise the hydropower production function with only logarithmic‐sized binary variables of the traditional methods and maintain high accuracy. The method is then applied to optimising the operation of the Lancang River Basin hydropower system, which has 13 head‐dependent reservoirs with a deterministic model and a two‐stage stochastic model. The results show that the authors' method significantly outperforms conventional linearisation methods and can obtain accurate solutions within an acceptable time for deterministic and stochastic large‐scale hydropower reservoirs operation optimisation problems.
An enhanced MPPT algorithm based on adaptive extremum‐seeking control applied to photovoltaic systems operating under partial shading
Authors: Silveira Rafaela Dizaró , das Neves Gabriel Pereira , da Silva Sérgio Augusto Oliveira , Angélico Bruno Augusto
Published: February 2021

This study presents an improved extremum‐seeking control (ESC) method, intended to optimise the maximum power point tracking (MPPT) in a photovoltaic (PV) generation system. More specifically, to overcome the problem associated with partial shading in PV systems that leads to multiple operating points, an adaptive loop based on the measured PV array power is added to the conventional ESC. This procedure creates a variable amplitude of the perturbation signal and is able to accurately reach and track the global maximum power point (GMPP). The perturbation signal amplitude changes only when a predetermined power variation value is exceeded. As a result, this MPPT algorithm provides an efficient extraction of solar energy, avoids large oscillations in output response, and ensures the proper operation and performance of the system. The ESC theory is described in detail and the feasibility and effectiveness of the proposed approach are proved through simulation and experimental results. Furthermore, comparative tests show the proposed method's performance improvement, compared to the conventional ESC, evaluated in terms of convergence time, power oscillation in steady state, and accuracy to track the GMPP.
Logarithmic droop‐based decentralized control of parallel converters for accurate current sharing in islanded DC microgrid applications
Authors: P. Monica , M. Kowsalya , Guerrero Josep M.
Published: February 2021

Remarkable progress in distributed power generation invigorated research into DC microgrids using a controllable DC–DC converter contingent to the functionalities therein. The study explores the circulating current issue in a parallel‐connected DC–DC converter and its associated current‐sharing capability. Despite, the conventional droop being a promising solution with less control complexity, the current sharing is achieved at an expense of voltage drop. The prime objective of this research work is to design a control strategy that guarantees a minimized circulating current with proper current sharing for a parallel‐operated DC–DC converter. This paper puts forth a dual reference‐based control to alleviate the droop and load effects of the system. The primary reference is generated by considering the effect of a marginal change in the input power of the converters. The virtual resistance‐based droop technique utilizes the prime reference for secondary droop reference generation. A current sharing algorithm is designed to assimilate adaptability to the scheme running under a variable line and load parameters. The comprehensive approach to the proposed control strategy has the advantages of improved current sharing and voltage regulation. A parallel DC–DC converter with the proposed control mechanism was investigated using MATLAB/Simulink and validated experimentally.
Preliminary analysis of long‐term storage requirement in enabling high renewable energy penetration: A case of East Asia
Authors: Du Ershun , Jiang Haiyang , Xiao Jinyu , Hou Jinming , Zhang Ning , Kang Chongqing
Published: February 2021

Integrating a high penetration of renewable energy for developing sustainable and low‐carbon electric energy system is becoming a common trend around the world. Many studies have evaluated the energy storage requirement for accommodating variable renewable energy (VRE). However, in the situation of high renewable penetration, there will be a huge potential requirement of long‐term energy storage for addressing the seasonal energy imbalance between VRE and load demand. Thus, a key element of evaluating the storage demand in enabling high VRE penetration is identifying the timescales of storage needed and the economic combination of long‐term and short‐term energy storages. This is neglected in existing researches. In this study, we quantitatively analyse the role of long‐term seasonal storage in enabling high VRE penetration. A generation expansion planning model is formulated to optimise the least‐cost generation portfolio with a renewable penetration target. Based on the proposed model, an empirical analysis for East Asia in 2050 is performed. The results indicate that (1) long‐term storage contributes to addressing the long‐term energy imbalance issue, (2) the optimal duration time of long‐term storage is around 720 h (a month), and (3) the long‐term storage becomes economical when the renewable penetration is above 70% (54.2% VRE penetration).
A new method for current–voltage curve prediction in photovoltaic modules
Authors: Peña Rafael , Diez‐Pascual Ana M. , Díaz Pilar García , Davoise Lara Velasco
Published: February 2021

In this work, a new method for obtaining the current–voltage curve for crystalline silicon and thin‐film flat panels is presented. It is based on the single‐diode model, with a variable shunt resistance and series resistance. New expressions for the shunt resistance and open circuit voltage as a function of the temperature and irradiance are deduced. Besides, a procedure to translate the series resistance to arbitrary conditions is proposed. The diode ideality factor and shunt resistance are obtained by optimization. The rest of the parameters that appear in the current–voltage curve are obtained from the module measurements by means of theoretical expressions. The procedure for obtaining the current–voltage curve under arbitrary operating conditions is also described. The results obtained with the developed model are compared with experimental measurements in cadmium telluride and amorphous silicon modules, and with results published in the literature for other technologies. The model faithfully reproduces the experimental values. For all the modules, the root mean square error for the maximum power is lower than 2% (below 1.5% in most cases). These errors are lower than those reported in the literature for other models. In particular, the results are significantly more exact in the case of thin‐film modules.
Control and optimisation of networked microgrids: A review
Authors: Islam Mojaharul , Yang Fuwen , Amin Mohammad
Published: February 2021

Microgrids (MGs) have become an integral part of smart grid initiatives for future power system networks. Networked microgrids consist of several neighbouring microgrids connected in a low/medium distribution network. The primary objective of a network is to share surplus/shortage power with neighbouring microgrids to achieve mutual cost‐effective operation, utilising green energy from renewable energy resources in the network and increasing the reliability of customer service. This article classifies networked microgrids on the basis of network formation and provides an overview of recent research on control of networked microgrids. In addition, a state‐of‐the‐art review of optimisation methods is provided to solve the energy optimisation problem in networked microgrids. Furthermore, the advantages and challenges of the networked operation of microgrids are presented as for possible research directions in the future.
A new parameter identification method of a dual‐rotor flux‐modulation machine based on an adaptive differential evolution algorithm
Authors: Mao Yuan , Niu Shuangxia , Yang Yun
Published: February 2021

With the wide applications of dual‐rotor flux‐modulation machines for the growing wind power generations, research activities for the control of dual‐rotor flux‐modulation machines are intensified in recent years. Most of the existing control schemes are based on indirect measurements of the d‐axis inductance, the q‐axis inductance and the stator resistance to achieve high torque density and low torque ripple for the dual‐rotor flux‐modulation machines. However, conventional measurements of the d‐axis inductance, the q‐axis inductance and the stator resistance may suffer from (i) low accuracy and (ii) additional sensor costs. To this end, an adaptive differential evolution algorithm is proposed to identify the machine parameters by considering the magnetic saturation and cross‐coupling issue at low rotational speed of dual‐rotor flux‐modulation machines. Finite element analysis is adopted in simulation to preliminarily monitor the actual machine parameter values based on the length and cross section area of the conductor and inductance matrix computation. Both simulation and experimental results reveal that the adopted adaptive differential evolution algorithm can identify the three parameters more steadily and accurately than the conventional genetic algorithm.
Plug‐in electric vehicles smart charging mechanisms for cost minimization and ancillary service provision
Authors: Aldhanhani Tasneim , Shaaban Mostafa , Al‐Durra Ahmed , El‐Saadany Ehab , Zeineldin Hatem
Published: February 2021

The increasing number of Plug‐in Electric Vehicles (PEV) connected to the grid will create challenges to be addressed and opportunities that can be ceased. One challenge is the load shape dynamics, which might result in increasing the loading level on the distribution lines. On the other hand, there is an opportunity to use the PEV stored energy to provide ancillary services to the grid. Therefore, this paper proposes a new PEV charging mechanisms that not only aid in ancillary service provision, but also help in reducing the charging cost and avoiding the extra investment in peak generation units while maximizing the integrated PEVs. The proposed approach utilizes three stages to ensure the satisfaction of PEV owners with different preferences and to respect the grid limitations. The main objective is to develop different charging mechanisms for charging PEV's in the parking lots to ensure the maximum satisfaction of the PEV owners by fulfilling their charging requirements with the minimum possible cost. The developed algorithm relies on a moving time window to address the real‐time changes and considers the participation of PEVs in the frequency regulation and peak shaving. The effectiveness of the proposed algorithm is verified through simulation using real data.
Sensing node selection and mobile sink displacement in the environments with multiple targets
Authors: Saadatdoost Leila , Motameni Homayun , Hosseini Andargoli Seyed Mehdi , Ghazalian Reza
Published: February 2021

In target tracking scenarios, a suitable sensor selection method in combination with designing mobile sinks (MSes) movement path is a promising solution to maximise the lifetime of the wireless sensor network (WSN). The lifetime optimization problem is non‐deterministic polynomial‐time hardness (NP‐hard) and its optimal solution requires an exhaustive search with the exponential complexity. To tackle this issue, the original problem is separated into two more tractable sub‐problems: first, the MSes' assignment and their positions' calculations, second, the SN assignment problem. The SNs assignment problem is an integer programing, which is relaxed to the more tractable form. Moreover, its solution results in a priority function which is combined with a numerical search algorithm to select the SNs. In the proposed framework, based on the estimated path of each target, a MS is assigned to the target. Besides, the MSes optimum position in the next rounds are calculated. Afterwards, for each target at each round, sensing nodes (SNs) are selected based on the targets' position and the MSes' position. Simulation results show that proposed solution increases the network's lifetime considerably in comparison with the benchmark algorithms while its complexity is much lower than that of the optimal exhaustive search algorithm.
The effect of the centrifugal acceleration on period spacings of gravito-inertial modes in intermediate-mass stars
Authors: Henneco J. , Van Reeth T. , Prat V. , Mathis S. , Mombarg J. S. G. , Aerts C.
Published: February 2021

Context. The Kepler and Transiting Exoplanet Survey Satellite (TESS) space telescopes delivered high-precision, long-duration photometric time series for hundreds of main-sequence stars, revealing their numerous gravito-inertial (g) pulsation modes. This high precision allows us to evaluate increasingly detailed theoretical stellar models. Recent theoretical work extended the traditional approximation of rotation, a framework to evaluate the effect of the Coriolis acceleration on g modes, to include the effects of the centrifugal acceleration in the approximation of slightly deformed stars, which so far have mostly been neglected in asteroseismology. This extension of the traditional approximation was conceived by re-deriving the traditional approximation in a centrifugally-deformed, spheroidal coordinate system.

Aims. We explore the effect of the centrifugal acceleration on g modes and assess its detectability in space-based photometric observations.

Methods. We implemented the new theoretical framework to calculate the centrifugal deformation of pre-computed 1D spherical stellar structure models and computed the corresponding g-mode frequencies, assuming uniform rotation. The framework was evaluated for a grid of stellar structure models covering a relevant parameter space for observed g-mode pulsators.

Results. The centrifugal acceleration modifies the effect of the Coriolis acceleration on g modes, narrowing the equatorial band in which they are trapped. Furthermore, the centrifugal acceleration causes the pulsation periods and period spacings of the most common g modes (prograde dipole modes and r modes) to increase with values similar to the observational uncertainties of the measured period spacing values in Kepler and TESS data.

Conclusions. The effect of the centrifugal acceleration on g modes is formally detectable in modern space photometry. The implementation of the used theoretical framework in stellar structure and pulsation codes will allow for more precise asteroseismic modelling of centrifugally deformed stars in order to assess its effect on mode excitation, trapping, and damping.
The intermediate neutron capture process
Authors: Choplin A. , Siess L. , Goriely S.
Published: February 2021

Context. Results from observations report a growing number of metal-poor stars showing an abundance pattern midway between the s- and r-processes. These so-called r/s-stars raise the need for an intermediate neutron capture process (i-process), which is thought to result from the ingestion of protons in a convective helium-burning region, but whose astrophysical site is still largely debated.

Aims. We investigate whether an i-process during the asymptotic giant branch (AGB) phase of low-metallicity low-mass stars can develop and whether it can explain the abundances of observed r/s-stars.

Methods. We computed a 1 M⊙ model at [Fe/H] = −2.5 with the stellar evolution code STAREVOL, using a nuclear network of 1091 species (at maximum) coupled to the transport processes. The impact of the temporal and spatial resolutions on the resulting abundances was assessed. We also identified key elements and isotopic ratios that are specific to i-process nucleosynthesis and carried out a detailed comparison between our model and a sample of r/s-stars.

Results. At the beginning of the AGB phase, during the third thermal pulse, the helium driven convection zone is able to penetrate the hydrogen-rich layers. The subsequent proton ingestion leads to a strong neutron burst with neutron densities of ∼4.3 × 1014 cm−3 at the origin of the synthesis of i-process elements. The nuclear energy released by proton burning in the helium-burning convective shell strongly affects the internal structure: the thermal pulse splits and after approximately ten years the upper part of the convection zone merges with the convective envelope. The surface carbon abundance is enhanced by more than 3 dex. This leads to an increase in the opacity, which triggers a strong mass loss and prevents any further thermal pulse. Our numerical tests indicate that the i-process elemental distribution is not strongly affected by the temporal and spatial resolution used to compute the stellar models, but typical uncertainties of ±0.3 dex on individual abundances are found. We show that specific isotopic ratios of Ba, Nd, Sm, and Eu can represent good tracers of i-process nucleosynthesis. Finally, an extended comparison with 14 selected r/s-stars show that the observed composition patterns can be well reproduced by our i-process AGB model.

Conclusions. A rich i-process nucleosynthesis can take place during the early AGB phase of low-metallicity low-mass stars and explain the elemental distribution of most of the r/s-stars, but cannot account for the high level of enrichment of the giant stars in a scenario involving pollution by a former AGB companion.
Genetic relationship between greisenization and Sn–W mineralization in vein and greisen deposits: Insights from the Panasqueira deposit (Portugal)
Authors: Launay Gaëtan , Sizaret Stanislas , Lach Philippe , Melleton Jérémie , Gloaguen Eric , Poujol Marc
Published: February 2021

The W–Sn Panasqueira ore deposit is a magmatic-hydrothermal system, which includes a high-grade quartz-vein type mineralization and a disseminated greisen-type mineralization occurring in the upper part of the Panasqueira two-mica granite. We investigated the genetic and chronological relationships between the greisenization of the Panasqueira granite and the formation of ore-bearing quartz veins by monitoring major and trace elements variations in quartz-white mica assemblages composing the two-mica granite, greisen and W–Sn-bearing quartz veins. The greisen is characterized by an overall depletion in Mg, Ti, Ca, Na, Ba, Sr, REE and enrichment in Fe, Li, Rb, Cs, Sn, W which reflect the breakdown of feldspars and fluid-rock interactions with W–Sn-bearing fluids. White-mica from greisen and mineralized quartz veins are enriched in granophile elements (F, Rb, Cs, Li, Sn, W and Zn) compared to magmatic muscovite from the two-mica granite. Trace elements contents in quartz depict trends which show the progressive enrichment in Ge and B and depletion in Al, Ti and Li from magmatic to hydrothermal quartz that emphasize the progressive evolution and cooling of the magmatic-hydrothermal system of Panasqueira. Geochemical similarities between quartz-white mica assemblages from greisen and wolframite-bearing veins suggest that greisenization and the formation of mineralized veins result from the same hydrothermal event and derived from the same source of hydrothermal fluids. Apatite from greisen and quartz vein yielded U–Pb ages of 292 ± 10 Ma and 295 ± 5 Ma respectively confirming that greisenization and the formation of mineralized veins occurred roughly at the same time. These ages also overlap with the emplacement age of the Panasqueira granite (296 ± 4 Ma), indicating a temporal link between greisenization, W–Sn mineralization and granite crystallization. Temperatures of the magmatic-hydrothermal system constrained by Ti-in quartz thermometry depicts a cooling trend from magmatic quartz of granite (700–600 °C) to hydrothermal quartz of greisen (500–400 °C) and veins (450–350 °C). These results suggest that greisenization and the formation of W–Sn bearing quartz veins occurred at the magmatic-hydrothermal transition, during which orthomagmatic fluids rich in volatils, incompatible elements and W–Sn were exsolved during the final solidification stage of the Panasqueira two-mica granite.
Integrative taxonomy confirms that Gregarina garnhami and G. acridiorum (Apicomplexa, Gregarinidae), parasites of Schistocerca gregaria and Locusta migratoria (Insecta, Orthoptera), are distinct species
Authors: Florent Isabelle , Chapuis Marie Pierre , Labat Amandine , Boisard Julie , Leménager Nicolas , Michel Bruno , Desportes-Livage Isabelle
Published: February 2021

Orthoptera are infected by about 60 species of gregarines assigned to the genus Gregarina Dufour, 1828. Among these species, Gregarina garnhami Canning, 1956 from Schistocerca gregaria (Forsskål, 1775) was considered by Lipa et al. in 1996 to be synonymous with Gregarina acridiorum (Léger 1893), a parasite of several orthopteran species including Locusta migratoria (Linné, 1758). Here, a morphological study and molecular analyses of the SSU rDNA marker demonstrate that specimens of S. gregaria and specimens of L. migratoria are infected by two distinct Gregarina species, G. garnhami and G. acridiorum, respectively. Validation of the species confirms that molecular analyses provide useful taxonomical information. Phenotypic plasticity was clearly observed in the case of G. garnhami: the morphology of its trophozoites, gamonts and syzygies varied according to the geographical location of S. gregaria and the subspecies infected.
Micro-résonateurs en anneau pour la détection et l’identification de polluants
Authors: Nguyen Chi Thanh , Ledoux-Rak Isabelle
Published: February 2021

Parmi les capteurs optiques visant la détection d’espèces chimiques ou biologiques, les dispositifs basés sur des microrésonateurs présentent un intérêt spécifique: ils n’ont pas besoin de marqueurs fluorescents, et leur fabrication est peu coûteuse. Le présent article décrit un capteur de ce type, basé sur des guides en anneau immergés dans un circuit microfluidique, et donne une illustration de ses performances pour la détection d’ions lourds dans l’eau potable.
A lower bound on the global powerful alliance number in trees
Authors: Ouatiki Saliha , Bouzefrane Mohamed
Published: February 2021

For a graph G = (V, E), a set D ⊆ V is a dominating set if every vertex in V − D is either in D or has a neighbor in D. A dominating set D is a global offensive alliance (resp. a global defensive alliance) if for each vertex v in V − D (resp. v in D) at least half the vertices from the closed neighborhood of v are in D. A global powerful alliance is both global defensive and global offensive. The global powerful alliance number γpa(G) is the minimum cardinality of a global powerful alliance of G. We show that if T is a tree of order n with l leaves and s support vertices, then
$ {\gamma }_{{pa}}(T)\enspace \ge \enspace \frac{3n-2l-s+2\enspace }{5}$
. Moreover, we provide a constructive characterization of all extremal trees attaining this bound.
Tripartite game models in a dual-channel supply chain: competition and cooperation
Authors: Lou Zhenkai , Hou Fujun , Lou Xuming , Zhai Yubing
Published: February 2021

This paper considers tripartite games in a dual-channel supply chain which involves a manufacturer, an offline retailer and an online retailer. Both competition and cooperation issues are analyzed. In the competition model, a Stackelberg game between the manufacturer and two retailers and a Bertrand game between two retailers occur simultaneously. It is shown that the channel which attracts more consumers’ purchase preference is charged a higher wholesale price and it meanwhile declares a higher sales price. In the presence of revenue sharing, cooperation issues between the three participants are studied and the change of the revenue of each participant is analyzed when partial cooperation exists. Further, the definition of the optimum two-player coalition is proposed. We demonstrate that the channel which attracts more preference of consumers is definitely in the optimum coalition. The structure of the two-player coalition is analyzed. Finally, under revenue sharing and cost apportionments, the change of each participant’s profit is examined.
Wearables in der Schlaganfallmedizin
Authors: Baumgartner Christoph , Baumgartner Jakob , Pirker-Kees Agnes , Rumpl Elke
Published: February 2021

Unter Wearables versteht man in die Kleidung oder in tragbare Geräte integrierte Sensoren, die eine kontinuierliche Langzeitmessung von physiologischen Parametern, wie Herzfrequenz, Blutdruck, Atmung, Bewegung, Hautwiderstand usw. und/oder Bewegungsmustern ermöglichen. In der Schlaganfallmedizin eröffnen Wearables neue Optionen in der Diagnostik, Prävention und Rehabilitation.
Air circulation in a gastrointestinal light source box and endoscope in the era of SARS-CoV-2 and airborne transmission of microorganisms
Authors: Chaussade Stanislas , Ali Einas Abou , Hallit Rachel , Belle Arthur , Barret Maximilien , Coriat Romain
Published: February 2021

Background and study aims The role that air circulation through a gastrointestinal endoscopy system plays in airborne transmission of microorganisms has never been investigated. The aim of this study was to explore the potential risk of transmission and potential improvements in the system.

Methods We investigated and described air circulation into gastrointestinal endoscopes from Fujifilm, Olympus, and Pentax.

Results The light source box contains a lamp, either Xenon or LED. The temperature of the light is high and is regulated by a forced-air cooling system to maintain a stable temperature in the middle of the box. The air used by the forced-air cooling system is sucked from the closed environment of the patient through an aeration port, located close to the light source and evacuated out of the box by one or two ventilators. No filter exists to avoid dispersion of particles outside the processor box. The light source box also contains an insufflation air pump. The air is sucked from the light source box through one or two holes in the air pump and pushed from the air pump into the air pipe of the endoscope through a plastic tube. Because the air pump does not have a dedicated HEPA filter, transmission of microorganisms cannot be excluded.

Conclusions Changes are necessary to prevent airborne transmission. Exclusive use of an external CO2 pump and wrapping the endoscope platform with a plastic film will limit scatter of microorganisms. In the era of pandemic virus with airborne transmission, improvements in gastrointestinal ventilation systems are necessary to avoid contamination of patients and health care workers.
Outcomes in Unicameral Bone Cyst Management Utilizing a Decision Tree Algorithm Approach
Authors: Paez Conner J. , Grant Kenneth , Bomar James D. , Edmonds Eric W.
Published: February 2021

Objective To determine if utilization of a decision tree algorithm could improve the healing rate of unicameral bone cysts (UBCs).

Methods Creation of the decision tree algorithm was based on previous literature and assessment of our clinical practice. Demographic, treatment, and radiographic data were collected retrospectively. Radiographic healing was determined using the Neer classification. Healing rate, as well as clinical/radiographic characteristics, were compared based on adherence to the treatment algorithm.

Results Forty-seven subjects were included. Mean age at initial surgery was 10.0 ± 3.3 years in children following the algorithm and 9.1 ± 3.2 years in those deviating from the algorithm (p = 0.393). Follow-up was found to be similar among those following the algorithm (37.5 ± 15.8 months) and those deviating from the algorithm (45.2 ± 24.6 months), p = 0.38. Children who followed the algorithm healed at a rate of 75%, while children who deviated from the algorithm healed at a rate 67% (p = 0.552).

Conclusions Although we reject our hypothesis that a decision tree algorithm for the management of UBCs in the pediatric population could improve the healing rate, we believe that we uncovered some utility in applying an algorithm to this pathology. Our algorithm was designed to minimize risk to the child and maximize healing with the least number of surgical events. Treating surgeons should consider this proposed pathway to determine the best treatment and to help families understand that these lesions rarely heal with a single-event surgery.
A Rare Case of Wear Induced Complications after Cervical Disc Replacement
Authors: Roschke Elisabeth , von der Höh Nicolas H. , Dietz Andreas , Stingu Catalina Suzana , Gradistanac Tanja , Henkelmann Jeanette , Heyde Christoph-Eckhard
Published: February 2021

Wear-induced complications after cervical disc replacement (CDR) are rare. A literature review on this topic found only a few case reports. We present a case of late complications after
implantation of two cervical disc replacements, which resulted in infectious/abrasion-induced mixed-type inflammation with extensive osteolysis. The diagnostic workup, surgical therapy and
outcome are presented and discussed with a review of the recent literature.