bluuebunny/crossref_metadata_2025 huggingface dataset:
Legal Foundations of Macroprudential Policy
Authors: Keller Anat
Published: October 2020

Macroprudential policy focuses on the financial system as a whole, as distinct from individual institutions, and its objective is to limit the costs to the real economy from system-wide distress of the financial sector. This book offers a critical, contextual and comparative examination of the nature of macroprudential policy as an emerging legal domain. It explores why macroprudential policy is necessary and how best to design tailored legal, institutional and governance frameworks that support the various supervisory stages in macroprudential regimes. Questions addressed relate to the design of the macroprudential mandate and institutional structures, independence, transparency and accountability arrangements, the nature and limitations of macroprudential authorities' supervisory powers, as well as the challenges that are likely to be encountered during the generation, collection and analysis of data and the use of macroprudential tools. The book extends well beyond being a 'one-stop-shop' introduction on all aspects of macroprudential policy. It digs deeper and does the heavy lifting by analysing the unique features of macroprudential policy that set it apart from other policy areas; examining the pulling (and at times, contradicting) forces which affect it and surfacing its complex and evolutionary nature and the unique challenges confronting macroprudential authorities.In order to derive and capture the theoretical foundations of macroprudential policy and support the high-level suggestions made on how to operationalise it, the book draws on established scholarships from international law as well as theories developed in the Organisational Behaviour field. It presents and explains the law within the context of the most recent empirical research in economics, including research on the prevalent governance structure of macroprudential policy, its interaction with other policy areas and the effectiveness of macroprudential tools. The normative discussion in the book is also grounded in practical specificities through detailed critical analysis of macroprudential policy frameworks at the national level (UK and US), regional level (EU) and global level (FSB, IMF and BIS). Dr. Anat Keller is a Lecturer in Law at the Dickson Poon School of Law, King's College London, and a Research Fellow at the Centre for Data Analytics for Finance and Macroeconomics (DAFM) at King's Business School. She was previously a Teaching Fellow and a Visiting Lecturer in Law at University College London (2007-2016). She is also a qualified solicitor and serves as a Deputy Chief Examiner of the University of London. She is co-author of the book 'Law Relating to Financial Services' now in its 8th edition and has published numerous articles and chapters in peer-reviewed journals and edited collections focusing on macroprudential policy.
Earthquakes Reveal How Quickly the Ocean Is Warming
Authors: Kornei Katherine
Published: October 2020

By timing sound waves set in motion by earthquakes, scientists have estimated that the Indian Ocean is warming by roughly 0.044 K per decade.
Environmental Association of Burning Agricultural Biomass in the Indus River Basin
Authors: Usmani Moiz , Kondal Ashish , Wang Jun , Jutla Antarpreet
Published: October 2020

Intensification of smog episodes, following harvesting of paddy crops in agricultural plains of the Indus basin in the Indian subcontinent, are often attributed to farming practice of burning standing stubble during late autumn (October, November) months. Biomass burning (paddy stubble residual) is a preferred technique to clear farmlands for centuries by farmers in that basin. However, despite stable agricultural landholding and yield, smog is being increasingly associated with burning agricultural biomass, thus creating a paradox. Here, we show that the concentration of smog (NOx, PM2.5, SO2) in the ambient air exceeds the safe threshold limits throughout the entire year in the region. This study argues that agricultural biomass burning is an ephemeral event in the basin that may act as a catalyst to a deteriorated air quality in the entire region. Results further demonstrate that simultaneous saturation of air pollutants along with high ambient moisture content and low wind speeds following the monsoon season are strongly related to aggravated smog events. Findings from this study should help make holistic mitigation and intervention policies to monitor air quality for sustainability of public health in agricultural regions where farming activities are a dominant economic driver for society.
Exploring Hydrologic Model Process Connectivity at the Continental Scale Through an Information Theory Approach
Authors: Konapala Goutam , Kao Shih‐Chieh , Addor Nans
Published: October 2020

Exploring water fluxes between hydrological model (HM) components is essential to assess and improve model realism. Many classical metrics for HM diagnosis rely solely on streamflow and hence provide limited insights into model performance across processes. This study applies an information theory measure known as “transfer entropy” (TE) to systematically quantify the transfer of information among major HM components. To test and demonstrate the benefits of TE, we use the Framework for Understanding Structural Errors (FUSE) model to mimic and compare four commonly used HM structures, VIC, PRMS, SACRAMENTO, and TOPMODEL, across 671 catchments spanning a variety of hydrologic regimes in the conterminous United States. We explore connections between HM components and catchment landscape characteristics (e.g., climate, topography, soil, and vegetation) and characterize their nonlinear associations using distance correlation and Spearman correlation coefficients. Our results indicate that while the information transferred from precipitation to runoff is similar across model structures (likely as a result of calibration), the information transferred among other components can vary significantly from a FUSE structure to another. We find that aridity, precipitation duration and frequency, snow fraction, mean elevation, forest area, and leaf area index are often significantly associated with TE between the main HM components. We propose that the presence of meaningful nonlinear associations can be used to diagnose process representation in HMs. Our results highlight the necessity to enhance the conventional streamflow‐only calibration approach for a more realistic representation of water dynamics in the models.
Centennial‐Scale Shifts in Hydrophysical Properties of Peat Induced by Drainage
Authors: Liu Haojie , Price Jonathan , Rezanezhad Fereidoun , Lennartz Bernd
Published: October 2020

Hydrophysical properties of peat influence the partitioning of rainfall into infiltration versus runoff, determine water flow and solute transport patterns, and regulate the carbon and nitrogen cycles in peatlands. Compared with mineral soils, our understanding of hydraulic properties of peat soils is limited, especially of the temporal dynamics of peat properties. A data set of peat subsidence as well as the bulk density (BD) change rate following artificial drainage was assembled from the literature. The collected data cover a time period of up to 272 years of land drainage for forestry and agriculture in boreal and temperate climate zones. The results show that the subsidence rate and BD change rate, and hydrophysical properties of peat can be estimated based on land drainage duration and land use. The most severe shift in pore structure of peat occurs within the first 20 years of land drainage. Peatland drainage reduces macroporosity with pore diameter greater than 50 μm, but increases the volume of pores <5 μm. In the long term, peat thickness loss is responsible for more than 80% of water storage loss. In conclusion, the derived functions between subsidence rate, BD change rate, and drainage duration provide a new approach to estimate the hydrophysical properties of peat (pore structure, saturated hydraulic conductivity, specific yield, and soil water storage) on a centennial scale. The derived hydrophysical parameter values can be used for long‐term hydrological modeling, especially if measured hydraulic parameters of peat are not available.
Sensitivity of Simulated Mountain Block Hydrology to Subsurface Conceptualization
Authors: Rapp G. A. , Condon L. E. , Markovich K. H.
Published: October 2020

Mountain block systems are critical to water resources and have been heavily studied and modeled in recent decades. However, due to lack of field data, there is little consistency in how models represent the mountain block subsurface. While there is a large body of research on subsurface heterogeneity, few studies have evaluated the effect that common conceptual choices modelers make in mountainous systems have on simulated hydrology. Here we simulate the hydrology of a semi‐idealized headwater catchment using six common conceptual models of the mountain block subsurface. These scenarios include multiple representations of hydraulic conductivity decaying with depth, changes in soil depth with topography, and anisotropy. We evaluate flow paths, discharge, and water tables to quantify the impact of subsurface conceptualization on hydrologic behavior in three dimensions. Our results show that adding higher conductivity layers in the shallow subsurface concentrates flow paths near the surface and increases average saturated flow path velocities. Increasing heterogeneity by adding additional layers or introducing anisotropy increases the variance in the relationship between the age and length of saturated flow paths. Discharge behavior is most sensitive to heterogeneity in the shallow subsurface layers. Water tables are less sensitive to layering than they are to the overall conductivity in the domain. Anisotropy restricts flow path depths and controls discharge from storage but has little effect on governing runoff. Differences in the response of discharge, water table depth, and residence time distribution to subsurface representation highlight the need to consider model applications when determining the level of complexity that is needed.
Basin‐Scale River Runoff Estimation From GRACE Gravity Satellites, Climate Models, and In Situ Observations: A Case Study in the Amazon Basin
Authors: Chen Jianli , Tapley Byron , Rodell Matt , Seo Ki‐Weon , Wilson Clark , Scanlon Bridget R. , Pokhrel Yadu
Published: October 2020

River runoff is estimated as a water budget residual using Gravity Recovery and Climate Experiment (GRACE) terrestrial water storage time series, ERA5 reanalysis data, and precipitation observations for January 2003 through December 2015 for the Obidos upstream drainage basin and for the entire Amazon basin. Estimated runoff based on the water budget agrees remarkably well with in situ gauge observations at Obidos, especially at seasonal time scales, with nearly perfect phase agreement but slightly larger seasonal amplitude. The discrepancy in the seasonal amplitude may be attributed to underestimation of river gauge runoff during the wet season when water overflows the riverbanks. The ERA5 model appears to overestimate long‐term mean evapotranspiration in the Amazon by ~2 cm/month based on comparisons with precipitation and runoff observations. Using precipitation data based on satellites and gauge observations relative to gauge observations alone improved agreement between water budget runoff estimates and in situ runoff observations. Seasonal variations in ERA5‐simulated runoff are about twice as large as those from in situ observations and show a large phase lag as well. Water budget‐based runoff for the entire Amazon (~7,200 km3 averaged over the 13‐year period) is significantly larger than observed runoff (~5,700 km3) at Obidos and notably larger than previous estimates for the entire Amazon. These differences may be partly related to submarine runoff from the Amazon basin that cannot be captured by surface gauges.
Hydrological Basis of the Budyko Curve: Data‐Guided Exploration of the Mediating Role of Soil Moisture
Authors: Chen Xi , Sivapalan Murugesu
Published: October 2020

We present a data‐guided framework to explore the hydrological basis of the Budyko curve, focusing on the role of soil moisture in mediating the partitioning of precipitation into runoff and evaporation and the role of climate in this partitioning. The conceptual framework for the derivation of the Budyko curve builds on empirically based power law relationships for long‐term average scaled runoff (Q/P) and scaled evaporation (E/Ep), both as functions of long‐term average (equilibrium) soil moisture. A second component of the framework is an empirical power law relationship between equilibrium soil moisture and the aridity index, Ep/P. Combinations of these empirical power law relationships with the long‐term water balance equation give rise to a form of the Budyko curve, which is a close approximation to Budyko's original relationship and is mathematically similar to the Turc‐Pike equation, thus supporting the role of equilibrium soil moisture in giving rise to the Budyko curve. In the remainder of the paper, for special cases of the parameter values of the power law relationships, we independently derive both the soil moisture dependence on Ep/P as well as the Budyko curve itself that not only reproduces a new Budyko‐type curve, but can also explain the spread of the empirical data points away from the mean curve. The paper also raises fresh questions about how the empirical power law relationships that govern the soil‐mediated precipitation partitioning may have emerged and the role of vegetation in that mediation.
Effects of Downward Intrusion of Saline Water on Nested Groundwater Flow Systems
Authors: Zhang Xiaolang , Jiao Jiu Jimmy , Li Hailong , Luo Xin , Kuang Xingxing
Published: October 2020

Nested groundwater flow systems (NGFS) are commonplace in various hydrogeological environments, including endorheic basins and coastal aquifers. The subsystems of the NGFS can be spatially separated by streamlines around the internal stagnation points. At the discharge zones of the topographic depressions, saline water often emerges due to high evaporation in endorheic drainage basins or the combined effects of evaporation and intermittent seawater submersion in coastal areas. To date, there are limited studies that have considered the impact of local‐scale downward migration of saline plumes in the topographic depressions on the NGFS. In this study, the classic NGFS are revisited by considering saline water in their discharge zones. To quantify the effects of salinity in the discharge zones on the NGFS, scenarios of various salinities in the discharge zones are simulated. The displacements of the internal stagnation points are used to quantify the evolution of the NGFS in response to salinity changes in the discharge zones. The results show that, as the salinity in the discharge zones increases, the hydraulic gradient near the discharge zone can be significantly reduced, the internal stagnation points shift upward, and the local groundwater flow systems retreat upward so that their original spaces are replaced by intermediate or regional flow systems. The discharge zone is expanded, and the overall groundwater flow velocity magnitude of the entire system decreases with salinity. This study may shed light on the management of saline wetlands, for example, the control of groundwater salinization, evolution of saline groundwater basins, and seawater intrusion.
Probabilistic Numerical Modeling of Compound Flooding Caused by Tropical Storm Matthew Over a Data‐Scarce Coastal Environment
Authors: Zhang Ying , Najafi Mohammad Reza
Published: October 2020

The passage of a tropical storm, as the main driver of storm surge and high waves in many coastal regions, can also generate heavy rainfall and cause river overflow. The resulting combination of riverine, pluvial, and coastal flood hazard can result in catastrophic losses particularly in densely populated coastal environments. In this study, we characterize compound flooding caused by Tropical Storm Matthew and assess the significance and associated uncertainties of multiple contributing factors over a data‐scarce coastal region. A hydrological model combined with a simplified two‐dimensional hydrodynamic model are set up and validated to investigate the compounding effects of storm tide, wave runup, rainfall, and river overflow at the southern coast of Saint Lucia in the Caribbean Sea. Pléiades‐1 and Sentinel‐1 satellite imageries are used to determine the flood‐impacted areas. The analyses are performed based on deterministic and probabilistic approaches and the effects of uncertain boundary conditions and model parameters are investigated. Results show that the individual analysis of flood hazards, in isolation, can lead to substantial underestimation of flood risks. Heavy rainfall and wave runup are the most significant contributors to compound flooding in Saint Lucia. In addition, the interactions between seawater and streamflow can exacerbate riverine flood hazards particularly upstream of the river mouth. Communities in western Vieux Fort, and the Hewanorra International Airport, have high exposure to compound flooding, which is projected to intensify under climate change.
EZH2-dependent epigenetic modulation of histone H3 lysine-27 contributes to psoriasis by promoting keratinocyte proliferation
Authors: Zhang Tongmei , Yang Luting , Ke Yao , Lei Jie , Shen Shengxian , Shao Shuai , Zhang Chen , Zhu Zhenlai , Dang Erle , Wang Gang
Published: October 2020

Psoriasis is characterized by keratinocyte hyperproliferation. While significant progress has been made in understanding the molecular mechanism regulating the proliferation of keratinocytes, little is known about the epigenetic factors that control this process. EZH2 and EZH2 mediated trimethylation of histone H3 lysine 27 (H3K27me3) was previously shown ectopically expressed in carcinoma and mediated proliferation, thereby we sought to clarify the role of EZH2–H3K27me3 in the proliferation of psoriatic keratinocyte. Interestingly, we found that EZH2 and H3K27me3 were both overexpressed in the epidermis of psoriatic lesional skin compared to normal skin. In vitro, the expression of EZH2 and H3K27me3 was stimulated in human keratinocytes treated with mixture of psoriasis-related cytokines pool (TNF-α, IFN-γ, IL-17A, and IL-22). Knockdown of EZH2 significantly reduced keratinocyte proliferative activity. Results from mRNA microarray analysis suggested that Kallikrein-8 (KLK8) might be the target gene of EZH2 in psoriatic keratinocytes. Overexpression or knockdown KLK8 could partially reverse the abnormal proliferation of keratinocytes caused by knockdown or overexpression of EZH2. In vivo, the inhibitor of EZH2, GSK126 could ameliorate the imiquimod-induced psoriasiform lesion. These results suggest that EZH2 might be a therapeutic target for the treatment of psoriasis.
Comparison of pharmacokinetics of omega-3 fatty acid supplements in monoacylglycerol or ethyl ester in humans: a randomized controlled trial
Authors: Chevalier Laurie , Plourde Mélanie
Published: October 2020

Background

A diet low in omega-3 fatty acids (n-3 FA) results in low plasma concentrations of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), the two main long chain n-3 FA. n-3 FA supplements on the market are esterified in triglycerides (TG) or ethyl ester (EE); the latter is absorbed less than other esterification forms. The objective of this study was to test and compare the pharmacokinetics of n-3 FA esterified in monoacylglycerides (MAG), a predigested form, with the EE form.

Methods

This study was a randomized, double-blind, crossover, controlled, clinical trial. Ten men and ten women between 18 and 60 years old were recruited. Participants received a single oral dose of 3 g of n-3 FA esterified in EE or MAG. Eleven blood samples were collected over 24 h post-dose. Plasma total lipids were extracted, methylated, and analyzed using gas chromatography.

Results

After receiving the MAG form, plasma EPA and DHA peaked at a concentration 3 and 2.5 times higher, respectively, than with the EE form. When provided in MAG form, n-3 FA plasma concentration during the absorption phase was on average 3–5 times higher than in EE form. When n-3 FAs were provided esterified in MAG, their concentration 24 h post-dose was higher than in EE. Males had a lower n-3 FA plasma concentration than females when n-3 FAs were provided in EE but there was no sexe difference when provided in MAG.

Conclusions

Plasma concentration of DHA and EPA was higher when provided in MAG than EE form.
Polymorphism in natural alkamides from Aniba riparia (Nees) Mez (Lauraceae)
Authors: Vidal Laura Maria Teodorio , Bezerra Beatriz Pinheiro , Fonseca Jéssica Castro de , Mallmann Auriana Serra Vasconcelos , de Sousa Francisca Cléa Florenço , Barbosa-Filho José Maria , Ayala Alejandro Pedro
Published: October 2020

The elucidation of crystal structures of polymorphs of riparins I, II, and III combined with thermal analysis studies allowed the determination of the thermodynamic relationships between polymorphic pairs.
Two-dimensional stable Fe-based ferromagnetic semiconductors: FeI3 and FeI1.5Cl1.5 monolayers
Authors: Hu Y. , Gong Y. H. , Zeng H. H. , Wang J. H. , Fan X. L.
Published: October 2020

Two kinds of novel ferromagnetic semiconductors FeI3 and FeI1.5Cl1.5 have high Curie temperature (>77 K) and sizable MAE.
1D materials from ionic self-assembly in mixtures containing chromonic liquid crystal mesogens
Authors: Rodríguez-Abreu Carlos , Kolen'ko Yury V. , Kovnir Kirill , Sanchez-Dominguez Margarita , Shrestha Rekha Goswami , Bairi Partha , Ariga Katsuhiko , Shrestha Lok Kumar
Published: October 2020

One-dimensional materials including carbon nanofibers can be produced from the ionic self-assembly of porphyrin-based chromonic mesogens.
Regeneration mechanism of a deactivated zeolite-supported catalyst for the combustion of chlorinated volatile organic compounds
Authors: Sun Pengfei , Chen Jingkun , Zai Shuaiying , Gao Shan , Weng Xiaole , Wu Zhongbiao
Published: October 2020

Industrial catalysis is confronted with the common problem of catalyst deactivation.
Local spring effect in titanium-based layered oxides
Authors: Su Heng , Guo Gencai , Ren Yang , Yu Xiqian , Zhang Xu , Ma Tianyuan , Lu Yue , Zhang Zihe , Ma Hao , Sui Manling , Li Hong , Sun Chengjun , Chen Zonghai , Xu Guiliang , Wang Ruzhi , Amine Khalil , Yu Haijun
Published: October 2020

The local spring effect in titanium-based layered oxides can release stress well during the cycling process and enhance the battery cycle performance.
Preparation of single-crystal metal substrates for the growth of high-quality two-dimensional materials
Authors: Li Yanglizhi , Sun Luzhao , Liu Haiyang , Wang Yuechen , Liu Zhongfan
Published: October 2020

Recent advances on preparing single-crystal metals and their crucial roles in controlled growth of high-quality 2D materials are reviewed.
Engineering water splitting sites in three-dimensional flower-like Co–Ni–P/MoS2 heterostructural hybrid spheres for accelerating electrocatalytic oxygen and hydrogen evolution
Authors: Bao Jiehua , Zhou Yuming , Zhang Yiwei , Sheng Xiaoli , Wang Yanyun , Liang Shuang , Guo Chang , Yang Wei , Zhuang Tao , Hu Yingjie
Published: October 2020

Flower-like Co–Ni–P/MoS2 heterostructures enhance intrinsic catalytic activity towards the OER and HER.
Effect of cation arrangement on polaron formation and colossal permittivity in NiNb2O6
Authors: Wang Jian , Gao Dandan , Liu Huan , Xie Jiyang , Hu Wanbiao
Published: October 2020

The distinct structure, electronic configuration and dielectric properties of ordered and disordered NiNb2O6 are experimentally demonstrated.
Low‐profile dual‐polarised metasurface‐enabled antenna array for base‐station applications
Authors: Ji Shuang , Liu Changrong , Liu Xueguan , Yang Xinmi
Published: October 2020

This Letter presents a dual linearly polarised microstrip antenna for base station applications. Firstly, a dual‐polarised metasurface‐based antenna element employing differential feeding technology is proposed. The proposed antenna element achieves a simulated bandwidth of 11.6% for |S 11 | < −15 dB, mutual coupling better than 30 dB, and the cross‐polarisation discrimination level over 35 dB. Secondly, based on the antenna element, a 3 × 3 antenna array is eventually presented, which was fabricated and characterised. The measured bandwidth is 12% for |S 11 | < −10 dB, and the port‐isolation is over 25 dB. The superiorities of low‐profile and high port isolation indicate that the proposed design is a promising candidate for sub‐6G base‐station applications.
Secrecy outage probability analysis for RIS‐assisted NOMA systems
Authors: Yang Liang , Yuan Yongjie
Published: October 2020

In this Letter, the physical layer security for a novel reconfigurable intelligent surface (RIS)‐assisted non‐orthogonal multiple access (NOMA) system in a multi‐user scenario is investigated, where the authors consider the worst case that the eavesdropper also utilises the advantage of the RISs. More specifically, they derive analytical results for the secrecy outage probability (SOP). From the numerical results, they observe that the use of RISs can improve the secrecy performance compared to traditional NOMA systems. However, for the worst case that the received signals at the eavesdropper come from the RISs and source, increasing the number of intelligent elements on the RIS has a negative impact on the secrecy performance. At high signal‐to‐noise ratios, the system's SOP tends to a constant. Finally, the secrecy performance can be improved through group selection.
Cyber attacks in smart grid – dynamic impacts, analyses and recommendations
Authors: Amin B.M. Ruhul , Taghizadeh Seyedfoad , Rahman Md. Shihanur , Hossain Md. Jahangir , Varadharajan Vijay , Chen Zhiyong
Published: October 2020

Cyber attacks can cause cascading failures and blackouts in smart grids. Therefore, it is highly necessary to identify the types, impacts and solutions of cyber attacks to ensure the secure operation of power systems. As a well‐known practice, steady‐state analysis is commonly used to identify cyber attacks and provide effective solutions. However, it cannot fully cover non‐linear behaviours and cascaded blackouts of the system caused by dynamic perturbations, as well as provide a post‐disturbance operating point. This study presents a novel approach based on dynamic analysis that excludes the limitations of the steady‐state analysis and can be used in the events of various cyber attacks. Four types of common attacks are reviewed, and their dynamic impacts are shown on the IEEE benchmark model of the Western System Coordinating Council system implemented in MATLAB Simulink. Then, recommendations are provided to enhance the security of the future smart power grids from the possible cyber attacks.
Robust model predictive control with sliding mode for constrained non‐linear systems
Authors: Fesharaki Shekoofeh Jafari , Kamali Marzieh , Sheikholeslam Farid , Talebi Heidar Ali
Published: October 2020

This study proposes a tractable robust non‐linear model predictive control for constrained continuous‐time uncertain systems with stability guarantees. First, a sampled‐data model predictive control for the nominal system is designed to provide a desired performance. Then, a sliding mode control is designed to recover the nominal performance for the uncertain system. The sampled‐data model predictive control that is solved online includes the initial state of the model employed in the problem as a decision variable. By merging sampled‐data model predictive control and sliding mode control in between samples, the effect of the uncertainty, which is matched with the input, is reduced efficiently. The computational complexity of the proposed robust model predictive control is the same as for the model predictive control while the input and state constraints satisfaction and asymptotic stability of the closed‐loop system are achieved. To illustrate the effectiveness of the proposed approach, the controller is applied to a vehicle platooning system.
Equivalence of recursive three‐step filter and infinity augmented Kalman filter for linear discrete‐time stochastic systems with direct feedthrough
Authors: Ding Bo , Zhang Tianping
Published: October 2020

In this study, the recursive three‐step filter method introduced by Gillijns and Moor (2007) is proved strictly to be equivalent to the augment Kalman filter (AKF) when the covariance of process noise about the input approaches infinity. This result indicates that if the information about the exogenous input is unknown, the AKF can also be used to simultaneously obtain the state and exogenous input estimation. Numerical examples illustrate the authors' main results.
Analysis of faulted power system during simultaneous open conductor and ground fault
Authors: Tailor Dhaval Narendrabhai , Makwana Vijay Hiralal
Published: October 2020

To perform analysis of the simultaneous faults of transmission lines is one of the challenging tasks. Most of the algorithms fail to find the precise fault location under such conditions. An attempt is made in this study to analyse one of the simultaneous faults called open conductor and ground fault. The essential objective of this study is to derive generalised impedance equations to identify precise fault location during simultaneous open conductor and ground fault that occurred on a transmission line with the help of its equivalent sequence components network. The proposed method has less complexity for data processes unlike other methods such as advanced artificial intelligence, fuzzy logic, and neural networks. To validate the proposed method, simulations have been carried out using MATLAB/SIMULINK software on an existing different type of medium transmission line. Calculation results demonstrate the effectiveness of the derived equations claims around 95% accuracy to identify fault location. The proposed scheme also works very efficiently during more than one simultaneous open conductor and ground fault that occurred in the network. This study would be beneficial to the new researcher to analyse the behaviour of the network during the simultaneous fault having a basic knowledge of the formation of a sequential network for different types of faults.
Transient analysis of the active surge protection gap trigger process with lightning voltage impulse injection
Authors: Le Yangjing , Yao Xueling , Sun Jinru , Li Tianquan , Xu Wenjun , Chen Jingliang
Published: October 2020

An active gas surge protection gap (SPG) and its energy coupling trigger circuit were designed in this study. In the lightning voltage impulse test, the active SPG had better protection characteristics than the passive SPG. To investigate the influence of the trigger circuit on the protection characteristics, the transient voltage and current characteristics of each electrical component in the active coupling trigger circuit were discussed. The equivalent model of the active trigger circuit was established, and the correlation between the active SPG protection characteristics and the active trigger circuit parameters was derived. According to the relationship, the theoretical breakdown characteristics of the active SPGs can be obtained by MATLAB. The deviation between simulated results and experimental data was no more than 11%. Based on the simulation, the design principles of the active energy coupling triggering circuit were proposed, laying the foundation for the theoretical research and engineering application of active SPGs.
Primary and backup fault detection techniques for multi‐terminal HVdc systems: a review
Authors: Zain Yousaf Muhammad , Liu Hui , Raza Ali , Baber Baig Mirza
Published: October 2020

Fault detection and location estimation in a multi‐terminal high voltage direct current (MTdc) transmission system based on voltage source converter (VSC) technology plays a vital role in enabling the interconnection of renewable energy systems in Europe. In this study, a comprehensive overview of the development of fault detection and location estimation techniques in the area of VSC‐based MTdc network is given. The progress in various primary and secondary protection algorithms is introduced and compared in terms of high fault resistance, complexity, and communication. Besides, this study investigates the suitability of existing fault detection techniques, compares techniques, and highlights their shortcomings. Additionally, this study also suggests unconventional ways to improve backup protection techniques and discusses futuristic methods to improve the fault diagnosis process.
Nonlinear AVR for power system stabilisers robust phase compensation design
Authors: Kumar Ajit
Published: October 2020

Phase characteristics of the generator‐exciter‐power (GEP) system with a conventional automatic voltage regulator (AVR) varies significantly with operating condition (OCs). In this study, a novel modification in the conventional excitation controllers (first‐order AVR, ST1A and AC1A) is presented. The authors found that the GEP phase responses are robust over a wide range of OCs yielding a robust phase compensation design for power system stabiliser. Additionally, they observed improved small‐signal stability without affecting the transient stability. Simulation results are presented on SMIB, IEEE 39‐ and 68‐bus power systems, wherein a detail sub‐transient model of synchronous generator is considered.
Classification of arc fault between broken conductor and high‐impedance surface: an empirical mode decomposition and Stockwell transform‐based approach
Authors: Lala Himadri , Karmakar Subrata
Published: October 2020

The high‐impedance arc fault (HIAF) is a result of the interaction between the current‐carrying conductor and the high‐impedance surface. This study presents a detailed and comparative time‐frequency based analysis for the classification of different arcs, generated by the interaction of a broken conductor and different arcing surfaces. The real‐time arcing voltage signals are considered as the basis of the whole time‐frequency based analysis from a medium voltage distribution line. In this proposed approach, empirical mode decomposition (EMD) is used to study the real‐time arc voltage signals of various surfaces. The intrinsic mode functions obtained by the application of the EMD technique is used as the input to various machine learning techniques, which later successfully classifies different HIAFs from their harmonic footprints. The Stockwell transform (ST) is additionally applied to the same test cases, and the classification of the arc is performed using similar learning algorithms to get a quantitative view of both outcomes of EMD and ST towards the selection of appropriate signal processing technique and machine learning algorithm for the same.
Study on the thermal behaviour and non‐linear coefficient of the 10 kV ZnO surge arrester
Authors: Cai Li , Yu Wenbo , Wang Jianguo , Xu Zhiling , Zhou Mi , Fan Yadong
Published: October 2020

The thermal behaviour of the surge arrester is vital to assess its operational condition. The surge arrester usually shows a process of temperature rising during a long‐term operation, particularly after subjecting to a surge. Therefore, the research on the temperature characteristics of ZnO arresters contributes to achieve the goal of the performance changes of the ZnO arresters over different temperatures. In this study, based on four types of ZnO arresters from different factories, the variation of the volt–ampere curve, DC characteristic parameters and non‐linear coefficient of the whole ZnO arrester at different temperatures were analysed. The relationship between the temperature and non‐linear coefficients was obtained through the method of the extraction of the non‐linear coefficients. Through the multiple impulse current tests, the temperature of the arrester was well calculated by measuring the corresponding volt–ampere curve, and the relationship between the surface temperature and V–I characteristics of the arrester is verified by the impulse test results. The obtained results provide a new idea for the application of the surface temperature of the arrester in the performance monitoring of the arrester.
Target distance measurement method using monocular vision
Authors: Jiafa Mao , Wei Huang , Weiguo Sheng
Published: October 2020

Most existing machine vision‐based location methods mainly focus on the spatial positioning schemes using one or two cameras along with non‐vision sensors. To achieve an accurate location, both schemes require processing a large amount of data. In this study, the authors propose a novel method, which requires much less amount of data to be processed for measuring target distance using monocular vision. Based on the geometric model of camera imaging, the parameters of the camera (such as camera's focal length and equivalent focal length.), as well as the principle of analogue signal being transformed into a digital signal, the authors derive the relationship among the target distance, field of view, equivalent focal length and camera resolution. Experimental results show that the proposed method can effectively and accurately achieve the target distance measurement.
Virtual charge‐based synchronisation and feedback linearisation‐based current control of a three‐phase grid‐connected inverter without grid voltage sensors
Authors: Roy Chowdhury Vikram , Kimball Jonathan W.
Published: October 2020

A conventional synchronous (rotating) reference frame control requires small‐signal models and introduces cross‐coupling terms. In this study, a virtual charge‐based scheme for grid synchronisation with only current measurements has been proposed for a three‐phase grid‐connected inverter with a first‐order filter. The methodology described in this study curbs the dependency of the inverter on the information of the grid voltage to generate unit vectors from the phase‐locked loop. This kind of estimation is especially important during grid voltage sensor failures or a distant point common coupling or weak grid conditions. In the proposed estimation scheme, no noisy differentiation is involved and only the nominal values of the interfacing filter parameters are utilised, making the implementation easier in digital microcontrollers. Also, a current control architecture based on feedback linearisation concept has been explored and embedded with the proposed grid voltage estimation technique, and the corresponding performance has been evaluated via simulation and experimental studies.
Low‐voltage ride‐through control for photovoltaic generation in the low‐voltage distribution network
Authors: He Yufei , Wang Minghao , Jia Youwei , Zhao Jian , Xu Zhao
Published: October 2020

The increasing penetration of photovoltaic (PV) energy in power grids will impose system instability issues, especially in the occurrence of faults. However, very limited research has been conducted on the low‐voltage ride‐through (LVRT) control of PV systems in the low‐voltage distribution networks (LVDNs) with predominantly resistive line impedances. To fulfil this remaining gap, the effects of active current injection (ACI) on the grid voltage support in LVDN is mathematically analysed in this study. Subsequently, a novel LVRT control scheme for the PV grid‐forming inverter is proposed, where the control distinguishes itself from other existing methods due to its optimisation of ACI and PV energy harvesting with the premise of system safety and specified reactive current injection as per grid codes. Multi‐mode control modes are involved in the proposed method for dealing with different environmental conditions and voltage dips. Meanwhile, the DC‐link voltage is adaptively operated in a self‐adjustable control structure for improving grid resilience. The effectiveness of the proposed control method is verified by simulations in MATALB Simulink and hardware experiments on a PV microinverter. Compared with the traditional LVRT control, the post‐fault power recovery and voltage support capability can be significantly improved.
Analysis, simulation and testing of the ZVRT capability of a wind turbine with a doubly fed induction generator
Authors: Cai Enyu , Liao Xiaozhong , Dong Lei , Li Yongzhan , Jiao Chong
Published: October 2020

Zero‐voltage ride through (ZVRT) is the extreme case of a low‐voltage ride through (LVRT), which represents the optimal grid‐connection capability of a wind turbine (WT). Enforcing ZVRT will improve the dynamic performance of a WT under the extreme conditions, and therefore significantly enhance the resiliency of a renewable‐rich power grid. Compared with LVRT, there are few research on ZVRT with no field validation been conducted. The feasibility of the ZVRT requirement, especially the 400‐ms‐level fault‐time condition, is not clear yet. The first system‐level study including the control strategy, transient analysis, hardware enhancement strategy, WT modelling and field test on the ZVRT capability of a Type‐3 WT is presented in this study. Particularly, to meet the challenging technical requirements, the authors proposed a hardware enhancement strategy, which accommodates with the widely‐used LVRT control approach. The holistic strategy is tested under the extreme grid‐connection condition by both simulation and a costly field test. The field test in the 400‐ms‐level fault‐time condition based on an operating WT in a weak power system directly verifies the feasibility and effectiveness of ZVRT for a Type‐3 WT. Furthermore, the critical time window and the key parameter ranges during ZVRT, which significantly affect ZVRT performance, are obtained.
Real‐time distributed economic dispatch scheme of grid‐connected microgrid considering cyberattacks
Authors: Huang Chongxin , Wang Jing , Deng Song , Yue Dong
Published: October 2020

Cyber security of microgrids attracts increasing attention since the relatively open communication network of the microgrids is vulnerable to hacker attacks. This study proposes a real‐time distributed economic dispatch scheme for the grid‐connected microgrid against the cyberattacks. Firstly, a virtual leader agent is placed at the point of common coupling to measure the real‐time power tracking error for achieving the power supply–demand balance, and then the optimal solution of the economic dispatch model is solved by the consensus algorithm of the multi‐agent system theory. Subsequently, a set of detection algorithms is designed for each generator to determine whether its neighbouring generators suffer from the cyberattacks. The attacked generator is gradually marginalised from the communication network through updating the weight in the communication adjacency matrix based on its reputation value, thereby the impact of the attacked generator on the whole system is reduced greatly. Finally, the numerical simulations are carried out to verify the effectiveness of the proposed cyberattack‐resilient distributed economic dispatch scheme.
Determining penetration limit of central PVDG topology considering the stochastic behaviour of PV generation and loads to reduce power losses and improve voltage profiles
Authors: Suliman Mohamed Saad , Hizam Hashim , Othman Mohammad Lutfi
Published: October 2020

Distributed generation (DG) has rapidly increased due to many technical, environmental and economical benefits. One of the DG application challenges is to find a proper area to incorporate the DG associated to a particular location. In this study, a central photovoltaic distributed generation (PVDG) topology is proposed to distribute the optimal sizes to the optimal locations. Uncertainties of load demand and renewable power generation are also taken into consideration of the optimisation problem. This study determines the deterministic and probabilistic penetration limits based on the distribution network topologies, considering the PVDG significant impact on active power losses reduction and voltage profiles improvement. The effectiveness of the proposed topology was validated on 33‐ and 69‐bus distribution networks adopting Monte Carlo simulation method, Newton‐Raphson load flow method and biogeography based optimisation. From the results, the voltage profiles, active power loss reduction, DG capacity required and penetration limit have shown better performances on the central PVDG topology over the bus dedicated PVDG topology.
Image retrieval using locality preserving projections
Authors: Putchanuthala Ramesh Babu , Reddy E. Sreenivasa
Published: October 2020

In web surfing, image retrieval algorithms play a vital role. Many algorithms are existing but they have their drawbacks and also low retrieval rates. Locality preserving projections is a novel method for image retrieval proposed in this study. As the method includes principal component analysis, nearest neighbour and eigen features in extracting the hyper parameters for classification, it has better retrieval rate. This novel approach is tested using the Yale facial image dataset and the performance of the algorithm is tested by using different classifiers like Decision Tree etc.
Orbital variability of the optical linear polarization of the γ-ray binary LS I +61° 303 and new constraints on the orbital parameters
Authors: Kravtsov Vadim , Berdyugin Andrei V. , Piirola Vilppu , Kosenkov Ilia A. , Tsygankov Sergey S. , Chernyakova Maria , Malyshev Denys , Sakanoi Takeshi , Kagitani Masato , Berdyugina Svetlana V. , Poutanen Juri
Published: October 2020

We studied the variability of the linear polarization and brightness of the γ-ray binary LS I +61° 303. High-precision BVR photopolarimetric observations were carried out with the Dipol-2 polarimeter on the 2.2 m remotely controlled UH88 telescope at Mauna Kea Observatory and the 60 cm Tohoku telescope at Haleakala bservatory (Hawaii) over 140 nights in 2016−2019. We also determined the degree and angle of the interstellar polarization toward LS I +61° 303 using two out of four nearby field stars that have Gaia’s parallaxes. After subtracting the interstellar polarization, we determined the position angle of the intrinsic polarization θ ≃ 11°, which can either be associated with the projection of the Be star’s decretion disk axis on the plane of sky, or can differ from it by 90°. Using the Lomb-Scargle method, we performed timing analyses and period searches of our polarimetric and photometric data. We found statistically significant periodic variability of the normalized Stokes parameters q and u in all passbands. The most significant period of variability, PPol = 13.244 ± 0.012 d, is equal to one half of the orbital period Porb = 26.496 d. The fits of the polarization variability curves with Fourier series show a dominant contribution from the second harmonic which is typical for binary systems with circular orbits and nearly symmetric distribution of light scattering material with respect to the orbital plane. The continuous change of polarization with the orbital phase implies co-planarity of the orbit of the compact object and the Be star’s decretion disk. Using a model of Thomson scattering by a cloud that orbits the Be star, we obtained constraints on the orbital parameters, including a small eccentricity e < 0.2 and periastron phase of ϕp ≈ 0.6, which coincides with the peaks in the radio, X-ray, and TeV emission. These constraints are independent of the assumption about the orientation of the decretion disk plane on the sky. We also extensively discuss the apparent inconsistency with the previous measurements of the orbital parameters from radial velocities. By folding the photometry data acquired during a three-year time span with the orbital period, we found a linear phase shift of the moments of the brightness maximum, confirming the possible existence of superorbital variability.