Current Asymmetry Research Articles

Changes in tide-induced asymmetries in a tidal creek by the presence of intertidal flats: The San Pedro Channel (Cadiz Bay)

A two-dimensional, non-linear, finite difference, hydrodynamic model was applied to the San Pedro channel (Cadiz bay) to study the changes on tidal current asymmetries along its course due to the reconnection of its main channel to a wide tidal lagoon that was artificially desiccated in the mid of 20th century. Results of both experimental in-situ data and model simulations show changes from a flood-dominance of current asymmetries when the channel was isolated, to a stronger and ebb-directed asymmetry after the reconnection to the upper lagoon. The influence of the upstream intertidal flats is revealed on the configuration of tidal current asymmetries induced by the mutual phase-lags between the M2 and M4 tidal constituents, as well as in the tide-induced residual currents. These effects were found to be stronger during spring tides. The impacts of current asymmetry reversal on the morphodynamics of coastal tidal environments and on water quality and pollutants transport are discussed.

Global Stock Market Volatility and Its Spillover on the Indian Stock Market: A Study Before and During the COVID-19 Period

This study investigates the impact of global stock market volatility on the Indian stock markets before and during the COVID-19 pandemic period. The study focuses on 11 stock markets, including Brazil, Canada, China, France, Hong Kong, India, Japan, Russia, Turkey, the UK, and the US, and applies the threshold generalized autoregressive conditional heteroskedasticity (TGARCH) model to capture the current asymmetry in returns influenced by past negative/positive shocks, and the diagonal Baba Engle Kraft Kroner (BEKK) model to examine the cohesion of the Indian equity market with global markets. The importance of the Indian stock market lies in its ability to provide capital to companies, attract foreign investment, and provide investment opportunities for both domestic and international investors. Data for the study was sourced from https://www.investing.com for the period September 2019 to September 2021 and Stata software was used for data analysis. The study finds that Brazil, Canada, France, Russia, UK, and the USA are the primary sources of financial weight on India’s stock returns. The results suggest that Indian investors can diversify their funds into other asset classes while restricting investments in these markets, particularly during downturns. Investors can make informed decisions to diversify their portfolio and minimize risk. The results can also benefit society by promoting a more stable and resilient financial system. The study can also be expanded to include other financial and economic indicators such as inflation and interest rates to provide a more comprehensive analysis of the impact of global market volatility on Indian equity markets.

Quantifying the ability of magnetohydrodynamic models to reproduce observed Birkeland current and auroral electrojet magnitudes

Although global magnetohydrodynamic (MHD) models have increased in sophistication and are now at the forefront of modeling Space Weather, there is still no clear understanding of how well these models replicate the observed ionospheric current systems. Without a full understanding and treatment of the ionospheric current systems, global models will have significant shortcomings that will limit their use. In this study we focus on reproducing observed seasonal interhemispheric asymmetry in ionospheric currents using the Space Weather Modeling Framework (SWMF). We find that SWMF does reproduce the linear relationship between the electrojets and the FACs, despite the underestimation of the currents’ magnitudes. Quantitatively, we find that at best SWMF is only capturing approximately 60% of the observed current. We also investigate how varying F10.7 effects the ionospheric potential and currents during the summer and winter. We find that simulations ran with higher F10.7 result in lower ionospheric potentials. Additionally, we find that the models do not always replicate the expected behavior of the currents with varying F10.7. This work points to a needed improvement in ionospheric conductance models.

On the Arctic Amplification of surface warming in a conceptual climate model

Over the last century Earth’s surface temperatures have warmed by order 1 K as a global average, but with significant variation in latitude: there has been most surface warming at high Northern latitudes, around 3 times more than in low latitude regions (termed Arctic Amplification), while there has been least warming over the Southern Ocean. Many contributing processes have been suggested to explain this asymmetrical latitudinal warming pattern, but quantification of the contributing factors responsible remains elusive. Complex general circulation climate models can reproduce similar asymmetrical patterns of warming, but it can be difficult to interpret the contributing processes. Meanwhile, idealised conceptual energy balance climate models have been able to reproduce a general polar amplification of warming whose origins can be interpreted, but this warming is often symmetrical across both hemispheres and may not be responsible for the real-world pattern. Here, we use a conceptual Energy Balance Model, with imposed closures for initial horizontal diffusivity and cloudiness drawing upon observational constraints and including temperature-dependent diffusivity and a sub-surface ocean heat reservoir, to show that the magnitude of present-day Arctic Amplification may arise through relatively simple thermodynamic (Clausius–Clapeyron) and radiative (climate feedback) processes. The current asymmetry between hemispheric warming may arise due to the transient heat transport up through the base of the surface ocean mixed layer from the slow-responding deep ocean to the fast-responding surface ocean being dominated by upwelling in the Southern Ocean. It should be noted that the processes identified here are not a unique in offering a potential solution, and so significant, or dominant, roles for dynamical processes remain plausible explanations for Arctic Amplification.

In light of #MeToo: reconsidering the art/artist relationship for better futures

This article reflects on the impact of #MeToo on the artworld. It examines some of the debates the movement spurred, such as censorship and whether or not we can separate the ‘man’ from ‘his’ work, with examples from recent curating around the world. The article uses feminist art history and theories of authorship to show that narratives of artistic temperament and genius are outdated but contribute to a society that indulges the perpetrators of #MeToo. It is demonstrated that the market’s investment in this art/artist relationship propagates a system of abuse. Alternative models of authorship are analysed to demonstrate that there are other ways of authoring and understanding art, which could radically shift current asymmetries and abuses of power. These include the anonymous Guerrilla Girls and the pseudonymous duo Bob and Roberta Smith. These artists toy with narratives of artistic genius and actively work against sexism in the artworld. The article concludes that we must still consider the biography when interpreting works – for the personal is part of #MeToo – but calls for a more holistic understanding of the artworld and its financial infrastructures in order to challenge its own apparatus.

Variations of cosmic ray intensity with the solar flare index, coronal index, and geomagnetic indices: Wavelet and cross correlation approaches

In this study, the cosmic ray stuff and its associations with the solar flare index, coronal index, and geomagnetic indices, such as Kp, auroral electrojets, Ap, disturbance storm time (Dst), polar cap, Lyman-alpha, Hp60, and Ap60 indices, were studied using wavelet-based approaches over KIEL and MOSC stations during 2003 and 2004. The cosmic ray data used in this study were obtained from ground-based neutron monitor stations. Different sources are also used to get data on the different indices used in this study. The yearly variation in cosmic ray intensity revealed that the intensity of cosmic rays over KIEL and MOSC stations was greater in 2004 and lower in 2003. This variation might be due to the ring current's asymmetry, which causes an enormous asymmetry in the storm-time cosmic-ray increase. The wavelet coherence transform shows a positive and negative correlation as well as cosmic ray lags with solar flares and coronal indices throughout different months of the 2003 and 2004 periods over both suggested stations. The results of cross correlation indicate that cosmic ray intensity is positively correlated with all geomagnetic indices. However, cosmic ray intensity was negatively associated with the Dst index during 2003 and 2004 over both suggested stations. Moreover, multi-resolution analysis and power spectral density (PSD) analysis are consistent with wavelet analysis. Using the PSD result, we have seen high-power wavelet regions during geomagnetically quiet months and low-power wavelets during disturbed months at a common frequency over both stations during 2003 and 2004.

Out to sea: ocean currents and patterns of asymmetric gene flow in an intertidal fish species.

Passive dispersal via wind or ocean currents can drive asymmetric gene flow, which influences patterns of genetic variation and the capacity of populations to evolve in response to environmental change. The mangrove rivulus fish (Kryptolebias marmoratus), hereafter "rivulus," is an intertidal fish species restricted to the highly fragmented New World mangrove forests of Central America, the Caribbean, the Bahamas, and Florida. Mangrove patches are biological islands with dramatic differences in both abiotic and biotic conditions compared to adjacent habitat. Over 1,000 individual rivulus across 17 populations throughout its range were genotyped at 32 highly polymorphic microsatellites. Range-wide population genetic structure was evaluated with five complementary approaches that found eight distinct population clusters. However, an analysis of molecular variance indicated significant population genetic structure among regions, populations within regions, sampling locations within populations, and individuals within sampling locations, indicating that rivulus has both broad- and fine-scale genetic differentiation. Integrating range-wide genetic data with biophysical modeling based on 10years of ocean current data showed that ocean currents and the distance between populations over water drive gene flow patterns on broad scales. Directional migration estimates suggested some significant asymmetries in gene flow that also were mediated by ocean currents and distance. Specifically, populations in the center of the range (Florida Keys) were identified as sinks that received migrants (and alleles) from other populations but failed to export individuals. These populations thus harbor genetic variation, perhaps even from extirpated populations across the range, but ocean currents and complex arrangements of landmasses might prevent the distribution of that genetic variation elsewhere. Hence, the inherent asymmetry of ocean currents shown to impact both genetic differentiation and directional migration rates may be responsible for the complex distribution of genetic variation across the range and observed patterns of metapopulation structure.

Identification and separation of baroclinic M4 current in estuaries

Tidal current asymmetry is a challenging issue in estuaries and is generally quantified based on the relative amplitude and phase of M4 constituents in semi-diurnal regions. Previous studies have focused on the barotropic M4 current (BTC), whereas baroclinic overtides are often ignored. Using field data and numerical simulation results, we established a separation method of the baroclinic M4 current (BCC), clarified its typical features in estuaries of large tidal range, and explored the mechanism of BCC from the perspective of frontogenesis. The results showed that a 180° phase reversal in the vertical direction and significant enhancement of the normalised amplitude were fundamental features of BBC. Meanwhile, a decrease in currents around the salt intrusion head may not be inevitable owing to the strong BTC induced by nonlinearity, especially in meso- or macro-tidal estuaries. In contrast, near the river plume, BCC may develop and be stronger than BTC. Furthermore, BCC leads to zero longitudinal net transport of water mass, as it is treated as an ‘oscillatory’ full-depth lock-exchange flow. Our findings present a framework for BCC in estuarine zones.

Study of electric power quality indicators by simulating a hybrid generation system

Currently, as part of the distributed generation paradigm, photovoltaic energy has a growing development. The diversity of the loads, their nonlinearity, and the penetration of the renewable energy sources (RES) cause a worsening of the energy quality indicators. The main quality indicators that affect hybrid photovoltaic systems are voltage and current harmonic distortion, voltage deviation, and voltage and current asymmetry in the system. The construction of physical and mathematical models in software applications, such as MATLAB, Simulink, and Simscape, makes it possible to simulate the operating conditions of these systems and determine the values of the indicators that account for the quality of the electric power supplied. In this work, the modeling and simulation of a photovoltaic system connected to the network that feeds a mixed industrial area are carried out to determine the indicators of energy quality.

0.38 kV Electrical Network With Three-phase Loads and Capacitor Shunt-balancing Device

The issue of reducing the current asymmetry coefficient and the current unbalance coefficient (in the absence of KSHSU, KSHSU in the load node, KSHSU on transformer buses) with the help of shunt-balancing devices is considered. The proposed symmetrical device has an additional two power stages and allows to increase the efficiency of symmetry due to adjustable, automatically changeable parameters that vary depending on the level of current asymmetry, i.e. on the magnitude of the zero sequence current.

A framework for estuarine future sea-level scenarios: Response of the industrialised Elbe estuary to projected mean sea level rise and internal variability

In this study, we apply probabilistic estimates of mean sea level (MSL) rise and a sub-set of regional climate model ensemble simulations to force a numerical model of the southern North Sea, downscaling projected sea level variability to the Elbe estuary that serves as a prototype for an industrialised meso-tidal estuary. The specific forcing combination enables a localised projection of future estuarine hydrodynamics accounting for the spread of projected global sea level rise and the spread of the regional climate projection due to internal variability. Under the applied high-emission scenario, the Elbe estuary shows high decadal rates of mean water level (MWL) rise beyond 19 mm y-1, increase in the tidal range of up to 14 mm y-1 and increase in extreme water levels of up to 18 mm y-1. The bandwidth of the estuarine response is also high. For example, the range of average monthly extreme water levels is up to 0.57 m due to the spread of projected global sea level rise, up to 0.58 m due to internal variability whereas seasonal range attains 1.99 m locally. In the lower estuary, the spread of projected global sea level rise dominates over internal variability. Internal variability, represented by ensemble spread, notably impacts the range of estuarine water levels and tidal current asymmetry in the shallow upper estuary. This area demonstrates large seasonal fluctuations of MWLs, the M2 tidal amplitude and monthly extreme water levels. On the monthly and inter-annual time scales, the MWL and M2 amplitude reveal opposite trends, indicative of a locally non-linear response to the decadal MSL rise enforced at the open boundary. Overall, imposed by the climate projections decadal change and MSL rise enhance the horizontal currents and turbulent diffusivities whereas internal variability locally mitigates sea level rise–driven changes in the water column. This work establishes a framework for providing consistent regionalised scenario-based climate change projections for the estuarine environment to support sustainable adaptation development.

Enhanced current density and asymmetry of metal–insulator–metal diodes based on self-assembly of Pt nanoparticles

Metal–insulator–metal (MIM) diodes facilitate rectification at high frequencies. However, the rectification ratio for light from visible to infrared spectra is insufficient. In this study, we developed a MIM diode with a strongly enhanced electric field achieved using the self-assembly of Pt nanoparticles (NPs) via atomic layer deposition. By shaping the tunneling barrier, current density and asymmetry were simultaneously enhanced by several orders of magnitude compared with the symmetric MIM diode. The diode efficiency of the proposed MIM diodes was experimentally demonstrated to be 231 times greater than that of the MIM diode without NPs. This strategy indicates significant potential for high-frequency rectification applicable in optical rectenna.

Impacts of river discharge, coastal geomorphology, and regional sea level rise on tidal dynamics in Pearl River Estuary

IntroductionRecently, accelerated sea-level rise (SLR) has raised major concerns on estuarine management and restoration because it modifies estuarine hydrodynamics, such as tidal inundation extent and amplitude, tidal current asymmetry, flood frequency, etc. Understanding underlying processes which regulate estuarine tidal dynamics is critical for mitigating potential impacts on the coastal population and development.MethodsWe selected the Pearl River Estuary (PRE), an estuary with a higher regional SLR compared to the global SLR as the study area. To identify the effects of regional SLR on tidal dynamics, we analyzed long-term records of four tidal variables from 19 gauge stations between 1952 and 2020, including annual highest tidal levels (AHTLs), annual lowest tidal levels (ALTLs), annual mean tidal ranges (AMTRs), and annual mean tidal levels (AMTLs).ResultsResults suggested that variability in tidal variables was site-specific. The AMTRs decreased gradually from offshore regions to the upper reaches of rivers with a maximum at the mouth of the estuary. In contrast, the magnitudes of the AHTLs, AMTLs, and ALTLs decreased when approaching the coastline. Distance to the coastline had the highest correlations with the AHTLs, ALTLs, and AMTLs, followed by river width and river depth. The local SLR was responsible for the temporal variability in AHTLs, ALTLs, and AMTLs at the estuarine mouth with correlation coefficients from 0.43 to 0.85 (P < 0.001) but showed low correlations with these three tidal variables at the upper reaches of rivers (P > 0.001). Instead, the tidal variables were highly correlated with river discharge at the upper reaches of rivers, especially for the AHTLs (correlation coefficient = 0.83, P < 0.0001).ConclusionsOur study demonstrated that the tidal dynamics demonstrate significant spatial-temporal variability. Geomorphology, river discharge, and sea levels have jointly affected estuarine hydrodynamics.

A device for detecting current asymmetry in a three-phase alternating current system

The article discusses the issues of identifying the asymmetry of currents in a three-phase alternating current system. The design of a current converter designed to detect the unevenness of the current load in parallel branches of the current lines of various power equipment is proposed. It is shown that a positive effect is achieved by making the magnetic circuit four-rod and the introduction of rectangular cutouts with modulating and output windings on two central rods of the magnetic circuit and it is possible to determine the unevenness of the current load of three parallel branches before (in three-phase AC circuits) or after rectifier-converter installations (in DC circuits), therefore, the functionality of the device for detecting current asymmetry is expanded.

Analysis and treatment of current unbalance abnormal situation of 750 kV double-circuit parallel transmission line

At present, the biggest problem faced by short-distance double-circuit parallel lines is the three-phase parameter asymmetry problem caused by non-transposition. This leads to three-phase current asymmetry, especially during heavy load performance is more prominent. Take a 750 kV double circuit parallel erection line in actual operation as an example, use EMTPE electromagnetic transient simulation software to simulate and analyze the current imbalance phenomenon. This paper studies the influence of phase sequence arrangement, distance between loops, distance between wires, line length, equivalent impedance, ground wire conditions and line power flow on current imbalance, and puts forward reasonable restraining measures. The simulation results show that when the line power flow is heavy, the double circuit lines are arranged in the same phase sequence and the distance between circuits is relatively short, there will be a large amplitude of zero sequence current on the line, mainly circulation current. If it is not suitable to adjust the protection measures, it can be considered to adjust the double-circuit lines to reverse phase sequence operation mode. The research results can provide reference for the engineering design of double-circuit parallel transmission lines.

Two‐Step Method for Determining the Solar Quiet Current Focus and the Validation Using Observing Procedure Experiment

AbstractIt was known that the Solar quiet (Sq) current is important for the ionosphere dynamics, which can cause variations in the geomagnetic fields recorded on the ground. Using a north‐south chain of observatories, the latitude of the Sq focus (center of the solar quiet current) can be determined in a local area. However, a single chain of observatories does not provide the longitudinal information of the Sq focus. In this study, we proposed an improved method using a magnetic observatory network in Asia to determine the focus automatically. After taking the variability and asymmetry of the Sq current into consideration, the proposed method determines the Sq focus with the longitudinal and latitudinal fitting processes. To verify the effectiveness of this method, we designed an observing procedure experiment (OPE) to simulate the geomagnetic field observation and focus determination under different conditions. The results show that the proposed method has the capability of tracking the trajectory of the Sq focus. Additionally, the OPE can efficiently validate the performance of the method.

Critical current asymmetry in HTS switches using iron-core electromagnets

Iron-core electromagnets are widely used as applied-field switches in high-temperature superconducting (HTS) flux pumps. It was recently reported that the critical current () of the HTS wire is suppressed by up to 45% in the air gap of the iron core. Here, it is reported that the self-field of a single tape (unifilar) is suppressed from 357 A to 195 A while in the air gap of an iron core, agreeing closely with the previous study. This is extended by showing that the response to a perpendicular magnetic field is asymmetric, with a peak of 249 A found to be at 0.16 T of applied magnetic field. This effect can be eliminated using an anti-parallel current configuration (bifilar), which is shown experimentally to recover close to the no-core self-field of 357 A with no observed asymmetry. The results of both types of switch configurations are closely replicated in finite-element modelling using COMSOL Multiphysics®. This is caused by the asymmetric interaction between the self-induced magnetic field of the HTS switch element and the magnetic circuit of the iron-core electromagnet.

Radial and Local Time Variations in the Thickness of Jupiter's Magnetospheric Current Sheet

AbstractThe magnetic field observations from the Galileo, Ulysses, Voyager 1 and 2, and Pioneer 10 and 11 spacecraft are analyzed to understand the structures and thickness of the Jovian magnetospheric current sheet. Using a new technique that can determine the motion of the spacecraft relative to the current sheet, we have built the first global map of the thickness of the Jovian magnetospheric current sheet. We show that the current sheet thickness in Jupiter's magnetosphere is not equal everywhere but changes systematically with both radial distance and local time. The extremely thin dawnside current sheet appears to be linked to the stresses imposed by the solar wind on the open magnetic flux housed in the lobes of the magnetosphere in that sector. We also show evidence of a mostly closed magnetosphere in the dusk sector. We show that the current sheet thickness asymmetries likely arise from a field and plasma convection system set up by the reconnection of the interplanetary magnetic field with that of Jupiter.

Incorporating exceptions and limitations to copyright law to incentivize the development of Artificial Intelligence in Latin America

In this paper, I describe the advantages and disadvantages of incorporating new Artificial Intelligence (AI)-enabling exceptions and limitations to the copyright laws of Latin American countries. Section 1 describes the threats and opportunities AI may pose to the region. Section 2 refers to the effects copyright legislation may have on investment decisions of AI firms, the potential benefits for countries incorporating them, Law & Economics and Comparative Law perspectives, and the current regulatory asymmetry in this matter across the region. Section 3 concludes with policy recommendations.

On the Mechanism behind the Variation of the Tidal Current Asymmetry in Response to Reclamations in Lingding Bay, China

Tidal current asymmetry, an important factor for waterborne substance transport, is strongly affected by the changing shoreline. Lingding Bay (LDB), located in the center of the Guangdong-Hong Kong-Macao Greater Bay Area, has suffered great shoreline changes since the 1970s. A well-validated numerical model is built to investigate how the changing shoreline impacts tidal current asymmetry, which is quantified by the skewness parameter. Two types of tidal current asymmetries, the flow velocity asymmetry (FVA) and the flow duration asymmetry (FDA), are considered here. Despite their different dominant combinations, the two asymmetries display a similar tendency from the mouth to the head of the LDB. When the shoreline changes due to successive land reclamation are taken into consideration, the FVA and the FDA alter correspondingly. The results suggest that the shoreline change shifts the FVA in Deep Bay (a side embayment of LDB) from ebb dominance to flood dominance, because of the changes of its dominant constituent combinations (K1/O1/M2 and the residual current). As the shoreline propagates seaward, the increasing contributions of M2/M4 and M2/S2/MS4 enlarge the water area of positive FDA (i.e., shorter duration of low water slack) in LDB. Analyses of tidal current asymmetries in Lingding Bay show that tidal current asymmetry has been enhanced by sustained land reclamation and will further impact sediment transport in the bay.