Study on Distribution Characteristics of Metro Stray Current and Evaluation of Cumulative Corrosion Effect

Stray current directly affects the regular operation of electrical equipment and facilities in the subway DC traction power supply system. Therefore, it is worthwhile to study the stray current distribution characteristics during train operation and the quantitative corrosion of buried pipelines. This paper introduces the traction characteristics of power carriages and power wheelsets of subway vehicles into the DC traction process. A finite element model considering the dynamic distribution of stray current under the actual operation of subway vehicles is established. The interference characteristics of stray current and the contribution of power sources under the multiparticle model are analyzed. The rail insulation damage caused by long service time and the quantitative calculation of rail and buried pipeline corrosion is considered. The model results show that the stray current in the buried pipeline under the multiparticle model is more accurate and more suitable for the protection in the actual subway. The quantitative corrosion of the buried pipeline is stronger than the partial insulation damage environment when the rail is not insulated. The rail and buried pipeline corrosion at both ends of the insulation damage position is relatively severe. The stray current distribution model established in this paper gives full play to the solution advantages of the finite element method and provides a new idea for the quantitative calculation of buried pipeline corrosion.

Expended range of Gomphonema firmum (Bacillariophyceae), once considered a Lake Baikal endemic, with notes on the identity of G. lanceolatum var. maximum

This note describes a new record of Gomphonema firmum Skvortzow, which expanded both morphological and distributional ranges of the species. This conspicuous diatom was previously unknown outside of Lake Baikal, where it inhabits deep-water areas. The newly discovered locality belongs to a small stream at a distance of 180 km west from Lake Baikal, where the species was found in a relatively high abundance that enabled to trace a size diminution series including specimens shorter than previously described. In addition, G. lanceolatum var. maximum Poretzky, a name for a diatom from Lake Teletskoe, was included in a synonymy of G. firmum that further expanded the species distribution. In the light of the presented data, the species appears to be a rare diatom with current distribution limited to a few scattered localities in southern Siberia.

Distribution of the European bladdernut Staphylea pinnata (Staphyleaceae) in Poland

This paper presents the current distribution range of the protected shrub European bladdernut Staphylea pinnata in Poland. The study was based on a literature review, multidisciplinary search methods and field visits. The paper presents 211 sites considered as natural (including 48 new) and 143 sites considered as sites of anthropogenic origin (including 116 new). The data included in this paper extend the natural range of the species mainly in the Sudety Mts & Sudety Foreland, Rożnów Foothills, and the Tarnogród Plateau. It has been confirmed that the areas of Przemyśl Foothills (54 sites) and Dynów Foothills (49 sites) are the sites most abundant in bladdernut considered as natural. A few sites of anthropogenic origin have been found in the area of northern Poland, several hundred kilometres from the border of the bladdernut continual distribution range. In the case of sites of anthropogenic origin, knowledge of their distribution has increased significantly. This paper provides a basis for further research on the bladdernut in Poland and Europe and may be useful in population management of this protected species.

First record of Cnemidochroma phyllopus (Coleoptera: Cerambycidae) in the province of Corrientes, Argentina and potential distribution in the southern part of South America

Cnemidochroma Schmidt, 1924, a small genus of the tribe Callichromatini endemic in South America, comprises six species of which the only one recorded in Paraguay, Uruguay, Argentina and Brazil is C. phyllopus (Guérin-Méneville, 1844). The aim of this study was to estimate potential suitable areas for C. phyllopus to provide further knowledge on its current distribution. A dataset of 43 records was compiled and species distribution modelling was employed linking these occurrences with bioclimatic variables. Results indicate higher suitability conditions along the Atlantic coast of Brazil, reaching north Uruguay and extending inland to Paraguay and northern parts of Argentina. In addition, we report a new distributional record from Corrientes, Argentina.

On the nature of self-field critical current in superconductors and its use as a probe of the superfluid density

<p>Superconductors are used in many applications where large electrical currents are needed. This is due to their ability to transport an electric current without resistance. There is however a limit to the magnitude of current that can be conducted before dissipation starts to occur. This is known as the critical current and is a topic of great interest in applied superconductivity. For type II superconductors, it is well known that vortex motion plays a role in the determination of the in-field critical current. This has led great effort in engineering the microstructure of these superconductors to hinder the motion of vortices and enhance their critical currents. However the self-field critical current (when there is no applied external field) generally does not see any enhancement due to efforts to pin vortex motion. The work here examines the behaviour of the self-field critical current in thin-film and cylindrical wire superconductors of many different superconductor types and sizes. It is found that a critical state is reached when the current density at the surface of the sample reaches the magnitude of Bc/μ₀λ for type I and Bc₁/μ₀λ for type II superconductors regardless of the size and material type. This finding shows that there is a fundamental limit to the self-field current density that cannot be enhanced by engineering the microstructure and is essentially of thermodynamic origin. The result also sets up the self-field critical current density as a probe of the superfluid density. This was explored in many different superconductor types by considering the temperature dependence of the self-field critical current. The ground-state magnetic penetration depth, groundstate energy gap and specific heat jump at the critical temperature were key thermodynamic parameters extracted from the critical current data. For a very large number of superconductors the extracted parameters in general matched well with literature values measured using conventional but much more complex techniques. A result inferred from the critical state was that the current distribution across the width of a rectangular superconductor would be uniform, contrary to expectations of the Meissner state. This was tested by measuring the perpendicular magnetic field resulting from a transport current in a superconducting tape as it reached the critical state. It was indeed found that the current distribution is uniform across the width. The self-field critical current was also measured in YBa₂Cu₃Oy samples with Zn impurities to measure the superfluid density and further test the self-field critical current as a measure of superfluid density and in particular explore whether it follows the canonical dependence on the transition temperature observed for superconductors with d-wave symmetry. Here the critical current was found to reduce as more impurities were added and indeed this matched its expected canonical reduction, following the superfluid density as Jc(sf) ∝p³/². These results taken together support the unexpected existence of a fundamental limit in the self-field critical current, which is thermodynamic in origin.</p>

On the nature of self-field critical current in superconductors and its use as a probe of the superfluid density

<p>Superconductors are used in many applications where large electrical currents are needed. This is due to their ability to transport an electric current without resistance. There is however a limit to the magnitude of current that can be conducted before dissipation starts to occur. This is known as the critical current and is a topic of great interest in applied superconductivity. For type II superconductors, it is well known that vortex motion plays a role in the determination of the in-field critical current. This has led great effort in engineering the microstructure of these superconductors to hinder the motion of vortices and enhance their critical currents. However the self-field critical current (when there is no applied external field) generally does not see any enhancement due to efforts to pin vortex motion. The work here examines the behaviour of the self-field critical current in thin-film and cylindrical wire superconductors of many different superconductor types and sizes. It is found that a critical state is reached when the current density at the surface of the sample reaches the magnitude of Bc/μ₀λ for type I and Bc₁/μ₀λ for type II superconductors regardless of the size and material type. This finding shows that there is a fundamental limit to the self-field current density that cannot be enhanced by engineering the microstructure and is essentially of thermodynamic origin. The result also sets up the self-field critical current density as a probe of the superfluid density. This was explored in many different superconductor types by considering the temperature dependence of the self-field critical current. The ground-state magnetic penetration depth, groundstate energy gap and specific heat jump at the critical temperature were key thermodynamic parameters extracted from the critical current data. For a very large number of superconductors the extracted parameters in general matched well with literature values measured using conventional but much more complex techniques. A result inferred from the critical state was that the current distribution across the width of a rectangular superconductor would be uniform, contrary to expectations of the Meissner state. This was tested by measuring the perpendicular magnetic field resulting from a transport current in a superconducting tape as it reached the critical state. It was indeed found that the current distribution is uniform across the width. The self-field critical current was also measured in YBa₂Cu₃Oy samples with Zn impurities to measure the superfluid density and further test the self-field critical current as a measure of superfluid density and in particular explore whether it follows the canonical dependence on the transition temperature observed for superconductors with d-wave symmetry. Here the critical current was found to reduce as more impurities were added and indeed this matched its expected canonical reduction, following the superfluid density as Jc(sf) ∝p³/². These results taken together support the unexpected existence of a fundamental limit in the self-field critical current, which is thermodynamic in origin.</p>

A Segmented Cell Measuring Technique for Current Distribution Measurements in Batteries, Exemplified by the Operando Investigation of a Zn-Air Battery

A transimpedance amplifier circuit as well as an instrumental amplifier circuit were used to measure current densities of a zinc-air battery with an integrated segmented current collector foil. Error calculation showed that the transimpedance amplifier is superior to the used instrumental amplifier, but both methods provide valuable and consistent results. They both showed comparable results with operando insight into the current distribution of the battery. The knowledge about those distributions is essential to avoid fast degradation of battery materials and irreversible capacity loss due to heterogeneous dissolution of the anode during discharge. In this work we showed that oxygen starvation as well as gas flow rate leads to large current gradients. It was also demonstrated that heterogeneous current distributions on cathode side induces also a heterogenous dissolution behavior on the anode, resulting in irreversible capacity loss.

Current distribution of Zostera seagrass meadows along the Bulgarian Black Sea coast (SW Black Sea, Bulgaria) (2010-2020)

The current distribution of Zostera spp. seagrass meadows along the Bulgarian Black Sea coast was studied. We used a combination of historical and recent observations of the habitat along the studied coastline. Remote sensing data (satellite images, sonar side-scans) was groundtruthed with georeferenced drop camera observations, scuba diving sampling and georeferenced scuba diving photo and video transects. Тhe total area of the habitat type ‘MB548 - Black Sea seagrass meadows on lower infralittoral sands’ (EUNIS habitat type list 2019) in the study area is 916.9 ha, of which only 17.9 ha are in man-made sheltered environments (harbours). All seagrass meadows identified in 1978-79 were also located during the current survey, despite the increased eutrophication pressure and overall degradation of benthic habitats in the W Black Sea during the 1980s and early 1990s.