bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic Reconnection in Three Dimensions: Observations of Electromagnetic Drift Waves in the Adjacent Current Sheet
Authors: Ergun R. E. , Hoilijoki S. , Ahmadi N. , Schwartz S. J. , Wilder F. D. , Burch J. L. , Torbert R. B. , Lindqvist P.‐A. , Graham D. B. , Strangeway R. J. , Le Contel O. , Holmes J. C. , Stawarz J. E. , Goodrich K. A. , Eriksson S. , Giles B. L. , Gershman D. , Chen L. J.
Published: November 2019

Magnetic reconnection at the subsolar magnetopause is persistently accompanied by strong fluctuations of the magnetic field (B), plasma density (n), and all components of the electric field (E) and current (J). The strongest fluctuations are at frequencies below the lower hybrid frequency and observed in a thin, intense current sheet adjacent to the electron diffusion region. In this current sheet, the background magnitudes of B and n are changing considerably, creating an inhomogeneous plasma environment. We show that the fluctuations in B and n are consistent with an oscillatory displacement of the current sheet in the surface normal direction. The displacement is propagating parallel to the magnetic reconnection X line. Wavelengths are on the order of or longer than the thickness of the current sheet to which they are confined, so we label these waves electromagnetic drift waves. E and J fluctuations are more complex than a simple displacement. They have significant variations in the component along B, which suggest that the drift waves also may be confined along B. The current sheet is supported by an electron drift driven by normal electric field, which, in turn, is balanced by an ion pressure gradient. We suggest that wave growth comes from an instability related to the drift between the electrons and ions. We discuss the possibility that drift waves can displace or penetrate into the electron diffusion region giving magnetic reconnection three‐dimensional structure. Drift waves may corrugate the X line, possibly breaking the X line and generating turbulence.
Strong Ground Motion Simulation of 2016 ML6.6 Meinong, Taiwan, Earthquake Using the Empirical Green's Function Method
Authors: Chen Ying‐Chi , Huang Huey‐Chu , Iwata Tomotaka , Asano Kimiyuki
Published: November 2019

The Meinong mainshock (ML6.6) occurred in southern Taiwan at 19:57:26.08 (UTC) on 5 February 2016. To study source characteristics of the mainshock, ground motions of the mainshock are simulated using the empirical Green's function method to construct a strong motion generation area (SMGA) source model. Records of the event occurred on 2 May 2010 (ML4.6) are chosen as the empirical Green's functions along with six strong motion stations surrounding the source area. Waveforms of the mainshock at all used stations are simulated utilizing the empirical Green's function method to construct a best‐fit source model by comparing the synthetic waveforms with the observed ones in the frequency range 0.2–10 Hz. The estimated SMGA is located on the NS‐striking fault plane. The size of SMGA is 7.2 km in length along the strike direction by 7.2 km in width along the dip direction. The rupture starts at the bottom left‐hand corner (i.e., southern bottom) of the SMGA and then extends radially toward the upper right‐hand corner with a rupture velocity of 2.6 km/s. The size of the SMGA and the rise time of the mainshock follow the self‐similar empirical relationship by Miyake et al. (2003, https://doi.org/10.1785/0120020183).
A Numerical Study of Convection Initiation Associated With a Gust Front in Bohai Bay Region, North China
Authors: Abulikemu Abuduwaili , Wang Yan , Gao Runxiang , Wang Yuan , Xu Xin
Published: November 2019

Convection initiation (CI) associated with a cold pool gust front (GF) of a mesoscale convective system (MCS) occurred in the Bohai Bay region, North China, is investigated using a real‐data, high‐resolution Weather Research and Forecasting model (WRF) simulation. Observations revealed that many CIs occurred successively near the GF, most of which developed significantly in both size and intensity and eventually merged with the MCS. The WRF simulation captured the general features of the CIs, GF, and MCS. Lagrangian vertical momentum budgets were conducted along the backward trajectories of air parcels within a convective cell initiated near the GF. The total vertical acceleration was decomposed into dynamic and buoyant components. The results showed that the dynamic acceleration played a decisive role for the CI, which can be further decomposed into five terms. The horizontal curvature term was rather small, with the height variation of air density almost zero. Although both vertical and horizontal extension terms played a positive role during the CI process, the vertical twisting term had the greatest contribution to the CI. This reflects the vertical tilting (to the forward of the GF) of an elevated updraft which was generated by the convergence of a forward‐tilting updraft at the GF leading edge and another airflow coming from ahead of the GF.
The Regional Hydroclimate Response to Stratospheric Sulfate Geoengineering and the Role of Stratospheric Heating
Authors: Simpson I. R. , Tilmes S. , Richter J. H. , Kravitz B. , MacMartin D. G. , Mills M. J. , Fasullo J. T. , Pendergrass A. G.
Published: November 2019

Geoengineering methods could potentially offset aspects of greenhouse gas‐driven climate change. However, before embarking on any such strategy, a comprehensive understanding of its impacts must be obtained. Here, a 20‐member ensemble of simulations with the Community Earth System Model with the Whole Atmosphere Community Climate Model as its atmospheric component is used to investigate the projected hydroclimate changes that occur when greenhouse gas‐driven warming, under a high emissions scenario, is offset with stratospheric aerosol geoengineering. Notable features of the late 21st century hydroclimate response, relative to present day, include a reduction in precipitation in the Indian summer monsoon, over much of Africa, Amazonia and southern Chile and a wintertime precipitation reduction over the Mediterranean. Over most of these regions, the soil desiccation that occurs with global warming is, however, largely offset by the geoengineering. A notable exception is India, where soil desiccation and an approximate doubling of the likelihood of monsoon failures occurs. The role of stratospheric heating in the simulated hydroclimate change is determined through additional experiments where the aerosol‐induced stratospheric heating is imposed as a temperature tendency, within the same model, under present day conditions. Stratospheric heating is found to play a key role in many aspects of projected hydroclimate change, resulting in a general wet‐get‐drier, dry‐get‐wetter pattern in the tropics and extratropical precipitation changes through midlatitude circulation shifts. While a rather extreme geoengineering scenario has been considered, many, but not all, of the precipitation features scale linearly with the offset global warming.
Alluvial Morphodynamics of Bedrock Reaches Transporting Mixed‐Size Sand. Laboratory Experiments
Authors: Jafarinik S. , Hernández Moreira R. , Viparelli E.
Published: November 2019

Research on the morphodynamics of bedrock rivers has primarily focused on bedrock incision, and little is known about the alluvial morphodynamics of rivers with exposed bedrock surfaces. More specifically, there is a lack of information on the morphodynamics of low slope bedrock reaches due to the recent recognition of such systems. Here, we present the results of laboratory experiments specifically designed to gain novel insight into flow resistances, flow hydrodynamics, and sediment transport processes in equilibrium partially exposed bedrock reaches transporting nonuniform sand as bed material in low slope areas. The experiments show that (1) downstream of a stable alluvial‐bedrock transition flow depth decreases in the streamwise direction, (2) bedform amplitude may decrease in the streamwise direction, and (3) stable patterns of downstream fining may form. Given the bedrock geometry, the water surface elevation at downstream boundary and the characteristics of the bedform regime in an alluvial channel subject to the same flow rate and sediment supply at equilibrium control bedform characteristics and sediment sorting patterns in the bedrock reach. When this distance is significantly smaller than the alluvial equilibrium flow depth or when the alluvial equilibrium bedform regime is close to the dune‐antidune transition, bedforms in the bedrock reach are closer to the dune‐antidune transition than at alluvial equilibrium with a consequent reduction in bedform amplitude. If the distance between the water level at the downstream boundary and the bedrock surface is close to the alluvial equilibrium flow depth and the alluvial equilibrium bedforms are well in the dune regime, a stable pattern of downstream fining can be expected. The comparisons between experimental and modeled sediment transport rates and equilibrium grain size distributions of the sediment further show that surface‐based bedload transport models derived for alluvial systems reasonably predict equilibrium sediment transport rates and bed surface size distributions in bedrock reaches if the presence of exposed bedrock is accounted for in terms of alluvial cover fraction.
The Hydraulic Geometry of Evolving Meandering Rivers
Authors: Monegaglia Federico , Tubino Marco
Published: November 2019

We study the bankfull hydraulic geometry of evolving meander bends. The analysis is driven by the recognition that none of the models introduced so far accounts for the conservation of the sediment mass, which leads to an unrealistic drop of the sediment transport capacity while the meander becomes longer. With this aim we propose a novel model to predict the adaptation of channel width and slope in evolving meanders, which is composed of a threshold relationship for the channel width and an ordinary differential equation for the slope, arising from an integral, meander‐averaged formulation of the Exner equation. The latter accounts for three main processes: (i) meander elongation, (ii) width change, and (iii) bed aggradation due to reduction of the transport capacity. Our model predicts a reduction of both channel width and slope, whose magnitude is regulated by the parameter
representing the ratio between the timescale of river planform and that of riverbed. When this ratio is large, the bankfull hydraulic geometry keeps nearly invariable; on the contrary, when
is small, as channel sinuosity increases, the bankfull width and slope experience a significant change. Through remote sensing analysis and published data we provide estimates of the parameter
for several meandering river reaches. We also trace the changes of the bankfull width of four dynamic meandering rivers in the Amazon basin by means of an innovative multitemporal bend‐scale analysis. Observed evolutionary trajectories are satisfactorily reproduced by theoretical predictions.
Road Crossings Increase Methane Emissions From Adjacent Peatland
Authors: Saraswati S. , Strack M.
Published: November 2019

We conducted a multi‐year study in two boreal peatlands to determine the impacts of resource access roads on methane (CH4) emission from adjacent peatland. Data were collected from transects aligned perpendicular to, and on both sides of two roads, one cutting through a bog and one cutting through a fen and from reference areas at each peatland. During the growing seasons of 2016 and 2017, we measured CH4 flux, water table, and peat temperature every second week. At the bog, the road associated impacts (changes to water table, peat temperature, and vegetation cover) were visible up to 20 m on both sides of the road (disturbed areas) with CH4 emission from disturbed areas being significantly higher compared to the reference areas in both years. There were no significant differences in CH4 emissions from disturbed areas compared to reference areas at the fen due to the limited hydrologic impact of the road crossing at this site. Bog plots located upstream of the road on transects located at >20 m from culverts and closer to the road emitted significantly more CH4 (124.6‐mg CH4·m−2·day−1) than other disturbed (10.2 mg CH4·m−2·day‐1) and reference areas (0.7‐mg CH4·m−2·day−1) due to shallower water table and warmer peat temperature. The road induced CH4 emissions (90.8 and 212.2 kg CH4/year for each kilometer of road, in 2016 and 2017, respectively) indicated that road construction across peatlands enhances CH4 emissions from these ecosystems, creating an additional source of anthropogenic greenhouse gas.
The Early to Middle Eocene Transition: An Integrated Calcareous Nannofossil and Stable Isotope Record From the Northwest Atlantic Ocean (Integrated Ocean Drilling Program Site U1410)
Authors: Cappelli C. , Bown P. R. , Westerhold T. , Bohaty S. M. , de Riu M. , Lobba V. , Yamamoto Y. , Agnini C.
Published: November 2019

The early to middle Eocene is marked by prominent changes in calcareous nannofossil assemblages coinciding both with long‐term climate changes and modification of the North Atlantic deep ocean circulation. In order to assess the impact of Eocene climate change on surface water environmental conditions of the Northwest Atlantic, we developed calcareous nannoplankton assemblage data and bulk stable isotope records (δ18O and δ13C) across an early to middle Eocene interval (~52–43 Ma) at Integrated Ocean Drilling Program Site U1410 (Southeast Newfoundland Ridge, ~41°N). At this site, early Eocene sediments are pelagic nannofossil chalk, whereas middle Eocene deposits occur as clay‐rich drift sediments reflecting the progressive influence of northern‐sourced deep currents. Between the end of Early Eocene Climatic Optimum (EECO) and the Ypresian/Lutetian boundary, calcareous nannofossils switched from an assemblage mainly composed of warm‐water and oligotrophic taxa (Zygrhablithus,Discoaster,Sphenolithus,Coccolithus) to one dominated by the more temperate and eutrophic reticulofenestrids. The most prominent period of accelerated assemblage change occurred during a ~2‐Myr phase of relatively high bulk δ18O values possibly related to the post‐EECO cooling. Although the dominance of reticulofenestrids persisted unvaried throughout the middle Eocene interval, early Lutetian (~47.4 to 47 Ma) stable isotope records indicate a reversal in the paleoenvironmetal trends suggesting a potential restoration of warmer conditions. Importantly, our data indicate that the ~2‐Myr interval immediately following the EECO was crucial in establishing the modern calcareous nannofossil assemblage structure and also reveal that the establishment ofReticulofenestra‐dominated assemblage occurred prior to the onset of persistent deep current system in the Northwest Atlantic.
Wettability Effects on Primary Drainage Mechanisms and NAPL Distribution: A Pore‐Scale Study
Authors: Molnar Ian L. , Gerhard Jason I. , Willson Clinton S. , O'Carroll Denis M.
Published: November 2019

The pore‐scale processes governing water drainage behavior in porous media have implications for geoscience multiphase scenarios including carbon capture and storage, contaminant site remediation, oil recovery, and vadose zone processes. However, few studies report directly observed pore‐scale water drainage phenomena in 3‐D soils. This knowledge gap limits our ability to verify assumptions underlying existing models and develop optimal solutions. This paper utilizes synchrotron X‐ray microtomography to present an experimental pore‐scale examination of nonaqueous phase liquid (NAPL)/water distribution along a primary drainage front as dense NAPL was injected upward into water wetting (WW) and intermediate wetting (IW) sand‐packed columns. Pore‐network structures were extracted from imaged data sets and mapped onto segmented NAPL/water data sets which allowed quantitative examinations of wettability impacts on (a) the extent to which NAPL fills individual pore bodies and (b) relationships between pore size and the phase occupying the pore, with both considered as a function of distance (and capillary pressure) relative to the NAPL front. These results revealed that several hypotheses treating IW sand similarly to WW sands are simplistic. IW systems exhibited a sequence of pore filling that deviated from traditional capillary pressure‐based model predictions: NAPL invades smaller pores, while larger, adjacent pores are bypassed leaving multipore residual water ganglia. NAPL pore saturations were close to 1 and did not change with capillary pressure in IW systems. Overall, the results illustrate how a relatively small change in operative contact angle alters NAPL distribution during water drainage, with important implications for geoscience multiphase flow scenarios.
Consistent MPFA Discretization for Flow in the Presence of Gravity
Authors: Starnoni M. , Berre I. , Keilegavlen E. , Nordbotten J. M.
Published: November 2019

A standard practice used in the industry to discretizing the gravity term in the two‐phase Darcy flow equations is to apply an upwind strategy. In this paper, we show that this can give a persistent unphysical flux field and an incorrect pressure distribution. As a solution to this problem, we present a new consistent discretization of flow, termed Gravitationally Consistent Multipoint Flux Approximation (GCMPFA), which is valid for both single‐ and two‐phase flows. The discretization is based on the idea that the gravitational term in the flow equations is treated as part of the discrete flux operator and not as a right‐hand side. Here, the traditional formulation representing pressure as a potential is extended to the case including gravity by introducing an additional set of right‐hand side to the local linear system solved in the MPFA construction, thus obtaining an expression of the fluxes in terms of jumps in cell‐center gravities. Numerical examples showing the convergence of the method are provided for both single‐ and two‐phase flows. For two‐phase flow, we show how our new method is capable of eliminating the unphysical fluxes arising when using a standard upwind scheme, thus converging to the correct pressure distribution.
On the Optimal Spatial Design for Groundwater Level Monitoring Networks
Authors: Ohmer M. , Liesch T. , Goldscheider N.
Published: November 2019

Effective groundwater monitoring networks are important, as systematic data collected at observation wells provide a crucial understanding of the dynamics of hydrogeological systems as well as the basis for many other applications. This study investigates the influence of six groundwater level monitoring network (GLMN) sampling designs (random, grid, spatial coverage, and geostatistical) with varying densities on the accuracy of spatially interpolated groundwater surfaces. To obtain spatially continuous prediction errors (in contrast to point cross‐validation errors), we used nine potentiometric groundwater surfaces from three regional MODFLOW groundwater flow models with different resolutions as a priori references. To assess the suitability of frequently‐used cross‐validation error statistics (MAE, RMSE, RMSSE, ASE, and NSE), we compared them with the actual prediction errors (APE). Additionally, we defined upper and lower thresholds for an appropriate spatial density of monitoring wells. Below the lower threshold, the observation density appears insufficient, and additional wells lead to a significant improvement of the results. Above the upper threshold, additional wells lead to only minor and inefficient improvements. According to the APE, systematic sampling lead to the best results but is often not suited for GLMN due to its nonprogressive characteristic. Geostatistical and spatial coverage sampling are considerable alternatives, which are in contrast progressive and allow evenly spaced and, in the case of spatial coverage sampling, yet reproducible coverage with accurate results. We found that the global cross‐validation error statistics are not suitable to compare the performance of different sampling designs, although they allow rough conclusions about the quality of the GLMN.
Supramolecular chirogenesis in zinc porphyrins by enantiopure hemicucurbit[n]urils (n = 6, 8)
Authors: Ustrnul Lukas , Kaabel Sandra , Burankova Tatsiana , Martõnova Jevgenija , Adamson Jasper , Konrad Nele , Burk Peeter , Borovkov Victor , Aav Riina
Published: November 2019

Chiral cyclohexanohemicucurbit[n]urils with multiple interaction sites induce chirality on planar zinc porphyrins and bind up to three porphyrin molecules.
Transport mechanism of water molecules passing through polyamide/COF mixed matrix membranes
Authors: Song Yang , Wei Mingjie , Xu Fang , Wang Yong
Published: November 2019

Mixed matrix membranes (MMMs) have gained significant attention due to their high water permeability without the cost of salt rejection. The mechanism of permeability promotion for PA/COFs MMMs is investigated in this work from molecular insights.
Ordered-vacancy-enabled indium sulphide printed in wafer-scale with enhanced electron mobility
Authors: Jannat Azmira , Yao Qifeng , Zavabeti Ali , Syed Nitu , Zhang Bao Yue , Ahmed Taimur , Kuriakose Sruthi , Mohiuddin Md , Pillai Naresh , Haque Farjana , Ren Guanghui , Zhu De Ming , Cheng Ningyan , Du Yi , Tawfik Sherif Abdulkader , Spencer Michelle J. S. , Murdoch Billy J. , Wang Lan , McConville Chris F. , Walia Sumeet , Daeneke Torben , Zhu Lianqing , Ou Jian Zhen
Published: November 2019

The unique and long-range ordered-vacancy structure in wafer-scale grown single-unit-cell-thick In2S3 facilitates excellent electronic performance.
Quasi-hydrophilic black silicon photocathodes with inverted pyramid arrays for enhanced hydrogen generation
Authors: Zhao Shuai , Yuan Guodong , Wang Qi , Liu Wenqiang , Wang Ru , Yang Shenghua
Published: November 2019

Randomly-distributed Si inverted pyramid arrays and CoS2 nanocrystals were synthesized on Si wafers for boosting photoelectrochemical water reduction.
Structure reorganization-controlled electron transfer of bipyridine derivatives as organic redox couples
Authors: Lv Yang , Liu Yiyang , Feng Ting , Zhang Jin , Lu Shanfu , Wang Haining , Xiang Yan
Published: November 2019

A lower reorganization energy could result in faster electron transfer due to a much smoother electron transfer process.
A 3D-printed ultra-high Se loading cathode for high energy density quasi-solid-state Li–Se batteries
Authors: Gao Xuejie , Yang Xiaofei , Wang Sizhe , Sun Qian , Zhao Changtai , Li Xiaona , Liang Jianwen , Zheng Matthew , Zhao Yang , Wang Jiwei , Li Minsi , Li Ruing , Sham Tsun-Kong , Sun Xueliang
Published: November 2019

A quasi-solid-state Li–Se battery assembled with an ultra-high Se loading of 20 mg cm−2 delivers the highest reported areal capacity of 12.99 mA h cm−2 at 3 mA cm−2.
SnO2 patched ultrathin PtRh nanowires as efficient catalysts for ethanol electrooxidation
Authors: Fan Xiaokun , Tang Min , Wu Xiaotong , Luo Shuiping , Chen Wen , Song Xing , Quan Zewei
Published: November 2019

The delicate combination between amorphous SnO2 patches and PtRh nanowires could enhance EOR activities and stability effectively.
Pick your precursor! Tailoring the size and crystal phase of microwave-synthesized sub-10 nm upconverting nanoparticles
Authors: Halimi Ilias , Rodrigues Emille M. , Maurizio Steven L. , Sun Hui-Qiao Tina , Grewal Manjot , Boase Emma M. , Liu Nan , Marin Riccardo , Hemmer Eva
Published: November 2019

The influence of precursor chemistry on thermal decomposition and particle growth in a rapid microwave-assisted strategy was investigated, demonstrating the selective synthesis of small and ultrasmall luminescent lanthanide-doped NaGdF4 nanoparticles.
Enhanced fuzzy C‐means clustering based cooperative spectrum sensing combined with multi‐objective resource allocation approach for delay‐aware CRNs
Authors: Sonti Siva Reddy , Prasad Mutchakayala Siva Ganga
Published: November 2019

In cognitive radio networks (CRNs), the resource allocation is viewed as a multi‐objective optimisation problem in terms of limitation of quality of service, the capacity of a channel and the transmitted power. To overcome these individual issues many researchers have been undertaken, but it does not solve the multi‐objective problems. In this study, the authors propose a multi‐objective random walk grey wolf optimisation (MORWGWO) algorithm to enhance the resource allocation in the CRNs. Here, they combined the spectrum sensing process with the resource allocation process. Initially, an enhanced fuzzy C‐means algorithm based cluster formation is proposed for spectrum sensing and then they model the resource allocation process and propose a MORWGWO algorithm for CRNs which generates the Pareto front inbetween of different objectives in a time‐efficient manner. The simulation result shows that the proposed method significantly enhances the network performance in terms of delay, delivery ratio, throughput, network lifetime, energy consumption, and fairness index. Result shows that the proposed method has a better throughput of 23.22, 15.09, 6.13% for varying nodes and 27.25, 10.62, 7.09% for varying data transfer rates while comparing with the multiple objective particle swarm optimisation, non‐dominated sorting genetic algorithm, and multi‐objective evolutionary algorithm.
Performance evaluation of combining SMT‐ETX metric with POS scheme for implementing multilayer multicast mobile ad hoc network (MANET) CRN
Authors: Kamal Sarab , Nazar Basma
Published: November 2019

In this study, the implementation of a multicast router protocol with a multilayer and multi‐hop consideration on the ad hoc CRN mobile was achieved through the use of a combined expected transmission count metric (ETX) with the Steiner minimal tree (SMT). The conjoined SMT‐ETX multicast CRN channel spectrums, which were used for measuring the availability of channels and the time required for data transmission from a given cognitive radio (CR) source to all of the CR destinations nodes was found to have resulted in the most efficient channel that was largely based on the possibility of success (POS) channel assignment scheme's probability success. Apart from demonstrating the best throughput and packet delivery rate performances for SMT‐ETX multicast CRN with POS scheme than those of the three multicast router protocol (MASA, MDR and RS) schemes with different primary users (PUs) traffic load and network parameters at Rayleigh fading channel, the SMT‐ETX multicast CRN with the decreasing PUs traffic load had also implied a higher chance of achieving the available secondary users channels in the CR network.
Retail market policy for distribution systems in presence of DERs and microgrids: comparison of sequential and simultaneous settlement of energy and reactive power markets
Authors: Homaee Omid , Zakariazadeh Alireza , Jadid Shahram
Published: November 2019

In this study, sequential and simultaneous clearing of energy and reactive power markets are investigated. In the sequential clearing, a model is proposed for reactive power market clearing in distribution systems. In this model, by using lost opportunity cost concept for distributed energy resources (DERs) that participate in reactive power market, the possibility of a win–win game for private owners of DERs and the operator of distribution network is provided. In addition, in this study, simultaneous markets for energy and reactive power are proposed. In order to investigate the proposed models, energy and reactive power markets are cleared sequentially and simultaneously in a 69‐bus typical distribution network in different scenarios and the results are compared together. The results evidenced that simultaneous clearing of reactive power and energy markets imposes less costs on the operator in comparison with the one in sequential clearing of reactive power and energy markets.
Faulty feeder selection and segment location method for SPTG fault in radial MMC‐MVDC distribution grid
Authors: Zeng Yu , Zou Guibin , Zhang Xin , Wei Xiuyan , Jiang Lingtong , Sun Chenjun
Published: November 2019

As a modular multilevel converter‐based medium‐voltage direct current (MMC‐MVDC) distribution grid mostly utilises small current grounding modes, the weak fault current for single‐pole‐to‐ground (SPTG) fault is very difficult to detect especially in the case of noises and fault resistance. Therefore, this study proposes a fast and accurate faulty feeder selection and segment location method. For SPTG fault, the transient current fault component is the charge–discharge current of distributed capacitance on the DC feeder. Analysis indicates that the waveforms of current fault component of positive and negative poles are negatively correlated for a faulty feeder; while they are positively correlated for a non‐faulty feeder. According to these characteristics, a faulty feeder selection criterion using Pearson correlation coefficient (PCC) is constructed. Then, utilising the energies difference between the current fault components of two poles, the faulty pole can be verified. In addition, the faulty segment is located by the PCC of the current fault component on both sides of each segment. Finally, simulation results confirm the validity of the proposed faulty feeder selection and segment location method.
Optimal design of hybrid DG systems for microgrid reliability enhancement
Authors: Yahaya Abass Afolabi , AlMuhaini Mohammad , Heydt Gerald Thomas
Published: November 2019

While the concept of microgrids and renewable energy systems is not entirely new, these integrated technologies have become a special topic of interest for researchers, utility providers and governments. Many challenges must be overcome to achieve better integration of renewable sources into the energy framework. This study presents some viable possibilities for the utilisation of a hybridised microgrid system. The hybridisation is achieved by an efficient design approach for the enhancement of both load and system reliability indices through the intelligent placement and sizing of hybrid distributed generation (DG) systems. Real‐time models of solar photovoltaics, wind turbines, batteries and thermal DGs are presented and implemented. Also, network component failures are stochastically modelled via Monte Carlo simulations, and a general tie‐set algorithm using an adapted breadth‐first search is proposed. Moreover, mixed‐integer multi‐objective particle swarm optimisation is employed, giving a four‐dimensional Pareto solution that is attained by optimising four reliability‐related objectives, namely system average interruption frequency index, System Average Interruption Duration Index (SAIDI), Energy Not Supplied (ENS) and total cost.
Charging coordination and load balancing of plug‐in electric vehicles in unbalanced low‐voltage distribution systems
Authors: Kikhavani Mohammad Reza , Hajizadeh Amin , Shahirinia Amir
Published: November 2019

Plug‐in electric vehicles (PEVs) are gaining popularity as a solution to reduce greenhouse gas production. On the other hand, uncoordinated charging of PEVs is a reason for grid stress and increasing congestion, total power consumption (TPC) and distribution lines and transformers losses. Moreover, single‐phase connection of electric vehicles in residential buildings causes line current imbalance and it has more negative effects on TPC and power losses. Thus, they are characterised as unbalanced loads with random locations, plug‐in times, charging rates, and durations. Hence, a charging coordination algorithm is proposed to utilise the integration of PEVs in both operational modes (grid‐to‐vehicle, vehicle‐to‐grid) to guarantee power loss reduction, voltage profile maintaining and load current balancing. The introduced algorithm can perform an optimal calculation to determine proper phase for PEVs in distribution feeders and decline the unbalancing by deploying a new device called phase switcher which is in series with chargers in residential buildings. The phase switcher is connected to the smart load management centre which uses the proposed algorithm to determine the proper phase for connection or disconnection of PEVs and finding the appropriate numbers of PEVs. To show the effectiveness of the proposed algorithm, simulation results are provided.
Flexible operation of grid‐connected microgrid using ES
Authors: Norouzi Mohammadali , Aghaei Jamshid , Pirouzi Sasan , Niknam Taher , Lehtonen Matti
Published: November 2019

This study presents a new solution to cope with the intermittent nature of renewable generations (RGs) and facilitate the integration of RGs in the smart active distribution network. Electric spring (ES) as one of the most influential solutions in demand‐side management is proposed as a flexible resource for flexible operation of grid‐connected microgrid against other sources of uncertainty such as forecasted load demand and energy price as well as the RGs output. This innovative approach has been considered in the context of a stochastic problem by presenting the static model of ES for the first time. The modelling of uncertainties is done by the roulette wheel mechanism as a scenario generation process and backward method for reducing the number of scenarios. In the proposed optimisation problem, the objective function is minimising the operating cost and voltage deviation as well as maximising system flexibility, subject to the AC power flow, ES and RGs constraints and technical system limitations. Finally, the proposed solution is tested on 33‐bus IEEE test system by the general algebraic modelling system software. The case studies demonstrate the efficiency of the proposed ES model in different simulation and experimental cases in providing flexi‐renewable microgrid.
New protection scheme for maintaining coordination time interval among relay pairs in micro‐grid by employing centralised master controller
Authors: Vijayachandran Vinod , Shenoy U Jayachandra
Published: November 2019

The penetration of distributed generators (DGs) of large capacities in micro‐grid introduces a considerable difference of current seen by the relay, during faults in its primary and backup region. This leads to several issues with the protection system such as relay miscoordination, delay in relay operation or failure in the relay operation (blinding). This study discusses a methodology to solve such issues by identifying the current status of micro‐grid configuration. The proposed method performs well by maintaining the coordination time interval (CTI) between the relays, irrespective of the source strength (weak or strong), the mode of operation of the micro‐grid (islanded or grid connected) or the micro‐grid configuration (radial or looped). The method proposes three curves with different settings in a single relay. A suitable algorithm has been developed to calculate the relay settings for all the three curves of each relay, well in advance and this program is made to run in the central master controller (MC). Thereafter, MC sends the settings of all relays through a reliable communication channel. The proposed relaying scheme provides desirable CTI margin as compared to conventional over current relay. The simulation results of the novel protection scheme are validated through hardware emulation.
Risk‐oriented PMU placement approach in electric power systems
Authors: Wang Shaobu , Huang Renke , Ke Xinda , Zhao Junbo , Fan Rui , Wang Hong , Huang Zhenyu , Sathanur Arun , Vrabie Draguna
Published: November 2019

The objective of traditional phasor measurement unit (PMU) placement approaches is to find the minimal number of PMUs to achieve full system observability. Very few consider the probability and the consequence severity of observability loss. For example, following cascading failures, lines are tripped, and the topology of the grid changes, which may result in observability loss for parts of the grid. With limited number of PMUs, it is desired that the PMUs should still sustain observability for the power grid after top‐severe cascading failures, other than after those cascading failures of low severity. To address the above issues related with the consequence severity of observability loss, this study proposes a risk‐oriented PMU placement approach. The proposed approach uses two indices, namely the probability of observability loss and the severity of its corresponding consequence to design the optimal PMU placement strategy. The authors show that the proposed approach is able to capture the critical events, while traditional approaches fail to do so. Extensive simulation results carried out on the IEEE 39‐bus and 118‐bus systems demonstrate the effectiveness of the proposed risk‐oriented approach.
Smart coordinated management of distribution networks with high penetration of PEVs using FLC
Authors: Zare Mohsen , Chabok Hossein , Niknam Taher , Azizipanah‐Abarghooee Rasoul
Published: November 2019

This paper is intended to give an effective coordination method between high penetration of plug in electric vehicles (PEVs) and optimal operation management (OOM) of distribution network problem. An effective fuzzy logic controller (FLC) is proposed which focuses on coordinated smart charge/discharge control of high penetration of PEVs with OOM in an iterative optimization process. In each iteration, the proposed FLC receives the voltage of the connection node of the PEVs, the remaining time to the peak load and the available energy of the PEVs while appropriately specifies the amount of absorbed or injected active power of the PEVs. This coordination leads to the minimization of the electric network losses, voltage flattening and reducing the produced pollutant. A modified version of Sine‐Cosine Algorithm (MSCA) is used to minimize the objective functions while the problem constraints are satisfied. An appropriate 33‐bus distribution network with 1000 PEVs in 100 groups is considered in order to show the authenticity and efficiency of this work. The results show that the proposed FLC‐based coordination procedure could effectively adjust the exchange power of the PEVs with the OOM decision variables in an acceptable time duration.
Autonomous energy community based on energy contract
Authors: Wang Yahui , Wu Xiaorui , Li Yong , Yan Ruifeng , Tan Yi , Qiao Xuebo , Cao Yijia
Published: November 2019

To effectively coordinate the distributed energy resources calls for reasonable energy management methods. Nowadays, there are a great number of studies about home energy management systems (HEMSs) and centralised control. However, the former has the problem of producing new peaks and valley when incentives are applied, and the latter only focuses on overall economic benefits and ignores individual preferences. Therefore, the authors take an emerging decentralised solution, i.e. peer‐to‐peer (P2P) energy sharing mechanism, into consideration and then propose an autonomous energy community model. In this P2P autonomous energy community, participants form an alliance and can trade energy with each other to maximisation individual benefit without a central controller. To allocate profit fairly among members, an energy contract based on Shapley values is proposed. Modelling of participants, implementation of energy contract and operation principle of community is presented in this study. Finally, case studies are conducted with the comparison of the model where households apply HEMS independently. The results show that the proposed model yields reduction in electricity cost and it is also friendly to the power grid with lower energy fluctuation compared with the counterpart.
Contribution of free iron particles to PD characteristics in flowing transformer oil at DC voltages
Authors: Luo Xinyu , Tang Ju , Pan Cheng , Zhang Yongze
Published: November 2019

Partial discharge (PD) characteristics of the transformer oil contaminated by metallic particles are relevant to particle movement. The motion characteristics of the particles will change when the oil flows, and hence, the PD characteristics differ from that in stationary oil. In this study, the PD characteristics were investigated at direct current voltages, and the particle trajectories were observed simultaneously. It was found that the number of discharges obviously decreased, but the discharge magnitude slightly increased as the oil flow speed increased. To explain the changes in the PD characteristics, a solid‐liquid two‐phase flow model was established to simulate the trajectories and the electric field distribution around particles. The experimental observations partially verified the simulated trajectories, which includes two stages, namely sedimentation and the subsequent oscillation‐collision stage. With the increase of the flow speed, the sedimentation particles decreased, and the horizontal spacing between two adjacent particle‐electrode collisions elongated. Therefore, the total collisions became infrequent, which reduced the number of discharges. Moreover, the higher the flow speed was, the slower the particle approached an electrode. Considering the discharge time lag, the distance between the particle and the electrode at the instant of the PD would increase, which increased the discharge magnitude.
Hybrid trading scheme for peer‐to‐peer energy trading in transactive energy markets
Authors: Khorasany Mohsen , Mishra Yateendra , Ledwich Gerard
Published: November 2019

This study proposes a hybrid energy trading scheme for peer‐to‐peer (P2P) energy trading in transactive energy markets. Market players can participate in different markets, including local markets, trading with neighbourhood areas, and traditional trading with the grid. In each local market, a community manager (CM) facilitates energy trading and negotiates with other CMs for neighbourhood trading. Based on the heterogeneous preferences of players of each community, each local market has a different price, which is different from market price for neighbourhood trading and trading with the grid. A distributed market clearing mechanism is presented that incorporates coordination among different markets. Also, a network utilisation charge function is defined to apply price signals to the market players to reflect network constraints in energy trading. These price signals are calculated based on the technical constraints in each market and are applied to the corresponding players based on their contribution to network constraints violation. Performance of the proposed trading scheme is evaluated against different market structures and through several case studies.
Wavelet transform modulus maxima‐based robust logo watermarking
Authors: Barr Mohammad , Serdean Cristian
Published: November 2019

Digital image watermarking is used to protect the copyright of digital images. In this study, a novel blind logo image watermarking technique for RGB images is proposed. The proposed technique exploits the error correction capabilities of the human visual system. It embeds two different watermarks in the wavelet/multiwavelet domains. The two watermarks are embedded in different sub‐bands, are orthogonal, and serve different purposes. One is a high capacity multi‐bit watermark used to embed the logo, and the other is a 1‐bit watermark which is used for the detection and reversal of geometrical attacks. The two watermarks are both embedded using a spread spectrum approach, based on a pseudo‐random noise sequence and a unique secret key. Robustness against geometric attacks such as rotation, scaling, and translation (RST) is achieved by embedding the 1‐bit watermark in the wavelet transform modulus maximacoefficients of the wavelet transform. The experimental results show that the proposed watermarking technique has better distortion parameter detection capabilities and compares favourably against existing techniques in terms of robustness against geometrical attacks such as RST.
Fast search real‐time face recognition based on DCT coefficients distribution
Authors: Hsia Shih‐Chang , Wang Szu‐Hong , Chen Chia‐Jung
Published: November 2019

The authors propose an adaptive face recognition algorithm based on the discrete cosine transform (DCT) coefficients approach. For the database's establishment, the face images are pre‐processed with colour transform, hair cutting, and background removing to eliminate non‐face information. The recognised kernel applied the weights of DCT coefficient distribution with the entire image transformation, to avoid position mismatch and reduce the light effect. The key coefficients of DCT are chosen from the training database by maximum variance. The fast search mode can reject 90% weak candidates with few coefficients to fasten the processing speed. The significant coefficients weighting methods are used to enhance face features. Only using 50 coefficients per picture, the recognition rate can achieve 95% for ORL face database testing. For real‐time recognition, camera imaging is processed with algorithms using C‐programming based on Windows system. The recognition rate can achieve 95% and the speed is about nine frames per second for real‐time recognition in practice.
Context‐based ensemble classification for the detection of architectural distortion in a digitised mammogram
Authors: Akhtar Yusuf , Mukherjee Dipti Prasad
Published: November 2019

The problem of computer‐aided detection of architectural distortion (AD) in a digitised mammogram has been attempted in this manuscript. In examining a mammogram, the decision regarding a particular region of interest (RoI) is dependent on the appearance of the surrounding regions. However, in existing methods to detect AD the inference about an RoI is dependent on the appearance of this RoI alone. In addition, multiple radiologists infer the same mammogram in coming to a final decision about the mammogram. Contrary to popular ensemble classifiers like Adaboost and Random Forest, the authors propose an ensemble based method (imitating multiple radiologists by classifiers) for detecting AD such that the decision on a test RoI is dependent on the decisions of the surrounding RoIs in the proposed ensemble classifier. The proposed context‐based ensemble classifier has been validated on two mammographic databases. The proposal shows promising results in both the databases.
Efficient inception V2 based deep convolutional neural network for real‐time hand action recognition
Authors: Bose S. Rubin , Kumar V. Sathiesh
Published: November 2019

The most effective and accurate deep convolutional neural network (faster region‐based convolutional neural network (Faster R‐CNN) Inception V2 model, single shot detector (SSD) Inception V2 model) based architectures for real‐time hand gesture recognition is proposed. The proposed models are tested on standard data sets (NUS hand posture data set‐II, Senz‐3D) and custom‐developed (MITI hand data set (MITI‐HD)) data set. The performance metrics are analysed for intersection over union (IoU) ranges between 0.5 and 0.95. IoU value of 0.5 resulted in higher precision compared to other IoU values considered (0.5:0.95, 0.75). It is observed that the Faster R‐CNN Inception V2 model resulted in higher precision (0.990 for APall, IoU = 0.5) compared to SSD Inception V2 model (0.984 for all) for MITI‐HD 160. The computation time of Faster R‐CNN Inception V2 is higher compared to SSD Inception V2 model and also resulted in less number of mispredictions. Increasing the size of samples (MITI‐HD 300) resulted in improvement of APall = 0.991. Improvement in large (APlarge) and medium (APmedium) size detections are not significant when compared to small (APsmall) detections. It is concluded that the Faster R‐CNN Inception V2 model is highly suitable for real‐time hand gesture recognition system under unconstrained environments.