Direct Currents Research Articles

ЧАСТОТА СОЧЕТАНИЯ КРАСНОГО ПЛОСКОГО ЛИШАЯ С СОМАТИЧЕСКОЙ ПАТОЛОГИЕЙ И МЕСТНЫМИ НЕБЛАГОПРИЯТНЫМИ ФАКТОРАМИ ПОЛОСТИ РТА

Background. In this article, we studied the frequency of combination of oral lichen planus with somatic pathology. The analysis of the survey, testing of individuals with oral lichen planus, laboratory blood counts; personalized advisory opinions of the local therapists. The influence of local adverse factors was studied by analyzing the indicators of galvanic current and the oral hygiene index.
 Objectives ― to study the frequency of combination of lichen planus with somatic pathology, the level of psycho-emotional status of patients, the role of local adverse factors in the oral cavity.
 Methods. There were analyzed two groups of patients in the age of 24―65 years. The main group (numbered in 22 people), included patients with oral lichen planus and control group (numbered in 15 people) combined people without pathology of the oral mucosa. The main group was divided into two subgroups I (numbered in 11 people), combined patients with a typical form of oral lichen planus and subgroup II (numbered in 11 people) included patients with an erosive-ulcerative form of oral lichen planus. Clinical and laboratory examinations were conducted by a local therapist to identify somatic pathology. Filled in the “health questionnaire” and tested by the method of Zung. Determined the concentration of glucose in blood; blood pressure indicators; the level of hygiene and galvanic current.
 Results. Questioning showed that patients with oral lichen planus have somatic pathology. Testing according to Zung's method revealed psycho-emotional disorders. Clinical and laboratory examination by a therapist revealed 100 % somatic pathology, concentration of glucose in blood and blood pressure in most individuals exceeded WHO standards. Analysis of the hygiene index showed a low level of oral hygiene; analysis of galvanometry revealed the presence of galvanic current in the oral cavity.
 Conclusions. Among all patients with oral lichen planus somatic pathology was detected in 100 % of cases. Lichen planus proceeds against the background of psycho-emotional disorders. Local unfavorable factors of the oral cavity (low level of hygiene and galvanic current) aggravate the course of lichen planus, slow down the regeneration.

Fast Multifrequency Measurement of Nonlinear Conductance

We describe a phase-coherent multifrequency lock-in measurement technique that uses the inverse Fourier transform to reconstruct the nonlinear current-voltage characteristic (IVC) of a nanoscale junction. The method provides for a separation of the galvanic and displacement currents in the junction, and easy cancellation of the parasitic displacement current from the measurement leads. These two features allow us to overcome traditional limitations imposed by the low conductance of the junction and high capacitance of the leads, thus providing an increase in measurement speed of several orders of magnitude. We demonstrate the method in the context of conductive atomic force microscopy, acquiring IVCs at every pixel while scanning at standard imaging speed.

Manganese Increases Lead Release to Drinking Water

Lead and manganese are regulated in drinking water due to their neurotoxicity. These elements have been reported to co-occur in drinking water systems, in accordance with the metal-scavenging properties of MnO2. To the extent that manganese is a driver of lead release, controlling it during water treatment may reduce lead levels. We investigated transport of lead and manganese at the tap in a full-scale distribution system: consistent with a cotransport phenomenon, the two metals were detected in the same colloidal size fraction by size-exclusion chromatography with multielement detection. We also studied the effect of manganese on lead release using a model distribution system: increasing manganese from 4 to 215 μg L-1 nearly doubled lead release. This effect was attributed primarily to deposition corrosion of lead by oxidized phases of manganese, and we used 16S rRNA sequencing to identify bacteria that may be relevant to this process. We explored the deposition corrosion mechanism by coupling pure lead with either MnO2-coated lead or pure lead exposed to MnO2 in suspension; we observed galvanic currents in both cases. We attributed these to reduction of Mn(IV) under anaerobic conditions, and we attributed the additional current under aerobic conditions to oxygen reduction catalyzed by MnO2.

Influence of heat treatment of the base material on the electrical properties of anisotyped heterojunctions n-ZnO:Al/p-CdZnTe

The conditions for the production of rectifying anisotyped heterostructures ZnO:Al/p-Cd1-xZnxTe by the method of RF-magnetron sputtering of ZnO:Al films onto crystalline substrates p-Cd1-xZnxTe were investigated. High energy parameters of the barrier were realized by preliminary heat treatment of the substrates. Mechanisms of forming direct and reverse currents through the heterojunction were set based on the analysis of temperature dependences of I–V-characteristics. Based on the researches of C–V-characteristics, the interconnection between physical processes during heat treatment was established, which makes possible to avoid the negative influence of the differences between crystalline materials lattices on the heterojunctions. Suggested models of energy diagrams of the manufactured heterostructures are well describe experimental electrophysical phenomena.

Modelación de una antorcha de plasma de arco no transferido

Las antorchas de plasma se usan para producir el plasma en la manufactura de materiales e industria energética, donde las antorchas de arco de corriente directa representan los componentes principales de los procesos con plasma térmico (plasma spraying, soldadura, corte de metales, tratamiento de residuos, producción de biogás, etc.). En una antorcha de plasma de arco no trasferido, se desarrolla un arco eléctrico aplicando una corriente directa entre el cátodo y el ánodo de la antorcha. Sucesivamente, el plasma se produce calentando, ionizando y expandiendo un gas alimentado a la antorcha antes de la región del cátodo. Los trabajos de laboratorio que usan técnicas de observación y de medición son de difícil aplicación, debido a las características físicas de estos fenómenos físicos. Así las técnicas computacionales pueden representar una herramienta valiosa para investigar los procesos con plasma, aunque el trabajo computacional es extremadamente desafiante, pues estos fenómenos son interdependientes y simultáneos. En este trabajo se propone un modelo computacional para simular una antorcha de plasma bidimensional de arco no trasferido en equilibrio termodinámico local. Se modelan condiciones de estado estacionario para las ecuaciones de conservación de mecánica de fluidos, trasferencia de calor y electromagnetismo en el software Comsol Multiphysics® 5.1. En la trasferencia de calor por radiación, el plasma se asume ópticamente fino y con un coeficiente de emisión neta. El flujo laminar de gas se modela con vórtice libre en la entrada para dos tipologías de antorchas axis-simétricas, respectivamente con argón y nitrógeno como gases de trabajo.

Non-Linear Control for Variable Resistive Bridge Type Fault Current Limiter in AC-DC Systems

This paper proposes a non-linear control-based variable resistive bridge type fault current limiter (VR-BFCL) as a prospective solution to ease the effect of disturbances on voltage source converter-based high voltage DC (VSC-HVDC) systems. A non-linear controller for VR-BFCL has been developed to insert a variable optimum resistance during the inception of system disturbances in order to limit the fault current. The non-linear controller takes the amount of DC link voltage deviation as its input and provides variable duty to generate a variable effective resistance during faults. The VSC-HVDC system’s real and reactive power controllers have been developed based on a current control loop where direct axis and quadrature axis currents are used to control the active and reactive power, respectively. The efficacy of the proposed non-linear control-based VR-BFCL solution has been proved with balanced as well as unbalanced faults. The results confirm that the oscillations in active power and DC link voltage have been significantly reduced by limiting the fault current through the insertion of an optimum effective resistance with the proposed control technique. The real time digital simulator (RTDS) has been used to implement the proposed approach. The performance of the proposed non-linear control based VR-BFCL is compared with that of traditional fixed duty control.

Corrosion behavior of two low alloy steel in simulative deep-sea environment coupling to titanium alloy

Corrosion behavior of two different low alloy steels (specimen 1, specimen 2) coupling to titanium (Ti) alloy was studied in simulative deep-sea environment with 500 m depths. Immersion tests revealed that the corrosion rate of specimen 1 was higher than that of specimen 2. The micro morphology showed all specimens of specimen 1 steel was susceptible to both intergranular and pitting corrosion. Electrochemical results imply that the galvanic current of specimen 1 was bigger than specimen 2, then decreased and stabilized at a small range after 15 h correspond. Finite element method was constructed to explain the development of the galvanic current density distribution with distance to the electrodes. The corrosion resistance of the alloy steels followed the order: specimen 2 > specimen 1 when coupling to Ti alloy.

Brain Modulation by Electric Currents in Fibromyalgia: A Structured Review on Non-invasive Approach With Transcranial Electrical Stimulation.

Fibromyalgia syndrome (FMS) is a complex disorder where widespread musculoskeletal pain is associated with many heterogenous symptoms ranging from affective disturbances to cognitive dysfunction and central fatigue. FMS is currently underdiagnosed and often very poorly responsive to pharmacological treatment. Pathophysiology of the disease remains still obscure even if in the last years fine structural and functional cerebral abnormalities have been identified, principally by neurophysiological and imaging studies delineating disfunctions in pain perception, processing and control systems. On such basis, recently, neurostimulation of brain areas involved in mechanism of pain processing and control (primary motor cortex: M1 and dorsolateral prefrontal cortex: DLPFC) has been explored by means of different approaches and particularly through non-invasive brain stimulation techniques (transcranial magnetic and electric stimulation: TMS and tES). Here we summarize studies on tES application in FMS. The great majority of reports, based on direct currents (transcranial direct currents stimulation: tDCS) and targeting M1, showed efficacy on pain measures and less on cognitive and affective symptoms, even if several aspects as maintenance of therapeutical effects and optimal stimulation parameters remain to be established. Differently, stimulation of DLPFC, explored in a few studies, was ineffective on pain and showed limited effects on cognitive and affective symptoms. Very recently new tES techniques as high-density tDCS (HD-tDCS), transcranial random noise stimulation (tRNS) and tDCS devices for home-based treatment have been explored in FMS with interesting even if very preliminary results opening interesting perspectives for more effective, well tolerated, cheap and easy therapeutic approaches.

Simple thermal control of dc low-current amplifiers improves stability

Measurement of direct currents below the nA range are common in nanoscience experiments. Gain and offset thermal drifts of high-gain (G to T) transresistance amplifiers limit the measurement sensitivity and accuracy. Here we describe a simple and inexpensive thermostat, constructed from off-the-shelf consumer components, and quantify the improvements in the gain and offset stability of a commercial transresistance amplifier (FEMTO mod. DDPCA-300), popular in nanoscience experiments.

Direct currents in power transformers

Abstract The article is devoted to the physical nature of geomagnetism, magnetic storms and methods of predicting their origin and deals with geomagnetic induced currents called GIC (Geomagnetically Induced Currents) and their effect on power transformers. A simplified, single-phase transmission system is described mathematically and its analysis was performed. Also the phenomenon of periodic semi-saturation of the magnetic circuit of the transformers resulting in current overload of the transformer windings, which can lead to thermal damage of the windings is explained. In addition, there is a significant deformation of the currents in the electrical system. The numerical solution of the system was verified by measurement on an electrical model.

Protection of personnel and patients in diagnosis and therapy with ionizing and non-ionizing radiation

Most of the sources used in physiotherapy use pulse magnetic fields; spark-discharges; radiofrequencies (RF); direct and low-frequency electric currents, electrical pulses; ultraviolet (UV) and infrared (IR) radiation; broad-spectrum lamps; lasers. The most relevant diagnostic sources are MRI scanners emitting static magnetic field, low-frequency fields, RF. The exposure of medical personnel to NIR depends on the type of transmitter, irradiation power, mode of operation, specific application, access of medical personnel to the treatment zone, shielding of the source and workplace, time duration of exposure. Devices for electric current therapy like pulses, ionophoresis therapy, vacuum therapy, emit magnetic field less than several μT. The devices for subthermal therapy emit RF energy up to 9,8 W/kg, compared to 0,4 W/kg basic restriction for whole body exposure. The average daily dose of the staff at 10 patients per day is 18,356 (V/m)2·h. The dose of medical personnel in protective chambers averaged per patient is WE = 23,88 (V/m)2·h. Regard to MRI equipment, the basic restrictions for static magnetic field for normal operating conditions exceed the action values for people at specific risk, also for risk of attracting ferromagnetic materials. In the case of the use of optical sources, power densities exceed the exposure limit values, and therefore the permissible stay is limited to minutes and seconds, and in some cases it is inadmissible. In cosmetic centers, sanatoriums and SPA centres, power densities are significant and some of them are not controlled (tanning beds and IPL systems). The laser systems applied in physiotherapy are mainly class 3R (visible range), which only pose a risk to the eyes, in some cases 1C. For some procedures, lasers of class 3B are also used which cause risk to the eye by intra-beam viewing as well as diffuse reflected radiation. In cosmetic centers where specific lamps and high class (4) lasers are used, there is a risk for serious skin burns and eye damage.

Extending the operational lifetimes of all-direct electron transfer enzymatic biofuel cells by magnetically assembling and exchanging the active biocatalyst layers on stationary electrodes

Enzymatic biofuel cells promise green power generation from a variety of natural resources, yet these systems all suffer from time-dependent degradation effects, in particular progressing inactivation of enzymes, which severely limit the operational lifetimes of such power sources. To extend operational lifetimes, we introduce a method to magnetically exchange exhausted enzymes for fresh ones. To this end, anodic and cathodic enzymes or enzyme cascades are immobilized on carbon coated magnetic nanoparticles. Under the action of suitable magnetic field gradients, these nanoparticles are assembled on the respective stationary electrodes, or released from the electrodes for collection and subsequent exchange. We demonstrate this method on a fructose/oxygen consuming biofuel cell employing fructose dehydrogenase and bilirubin oxidase as well as on anodic and cathodic cascades employing fructose dehydrogenase/invertase and bilirubin oxidase/catalase, respectively. The enzyme-modified nanoparticles support direct electron transfer bioelectrocatalytic currents by wiring the redox active cofactors to the carbonaceous coating and from there to the electrode surfaces. The facile injection, assembly, and removal of enzyme-modified magnetic nanoparticles along with fuel solution provides a promising approach to extend the operational lifetime of enzymatic biofuel cells without the need for exchanging entire systems including chambers and electrodes.

Galvanic Couple Behavior Between AA7050-T7451 and Stainless Steel in a Fastener Arrangement Assessed with Coupled Multi-Electrode Arrays Under Atmospheric Exposure Conditions

Dissimilar metal coupled multi-electrode arrays (CMEAs) of AA7050-T7451 and Type 316 stainless steel were utilized to investigate galvanic coupling behavior under atmospheric conditions, represented by thin electrolyte films and wet/dry cycling. CMEAs were used to analyze location specific galvanic current densities under both a simple flat geometry and in a simplified two dimensional (2D) representation of a fastener geometry. Cyclic wet/dry exposures on the flat CMEAs under 70 μm thin films increased the anodic charge density by over one order of magnitude relative to the 70 μm exposure of a flat CMEA under constant 98% relative humidity. During the wet/dry cycle, sharp current increases were observed upon the onset of wetting and drying attributed to the high Cl− concentration in the droplet and thin electrolyte layer. Using a CMEA arranged to represent a 2D representation of a fastener in a plate, the anodic charge for galvanic corrosion currents increased under a static 70 μm thin film of NaCl soluti...

Influence of Area Ratio and Chloride Concentration on the Galvanic Coupling of Copper and Carbon Steel

Carbon steel (CS) vessels coated with ∼3 mm of Cu have been proposed for the permanent disposal of used nuclear fuel in a deep geological repository (DGR) in Canada. In the event of an undetected defect in the Cu coating that exposes the underlying CS to groundwater, the possibility of galvanically accelerated corrosion of CS arises. In this work, the impact of O2 availability, NaCl solution concentration, and cathode:anode area ratio on the galvanic corrosion behavior of Cu/CS couples was evaluated by monitoring the galvanic potential of the couple and the galvanic current passing between Cu and CS. The corrosion products and surface damage were analyzed using Raman spectroscopy and SEM/EDX. Varying the Cu:CS area ratio from 1:1 to 2500:1, the [Cl−] from 0.001 to 3.0 M, the sparging gas from air to Ar, and monitoring the resulting changes in the galvanic current, galvanic potential, corrosion products, and surface damage showed that the galvanic corrosion of CS was most severe when it was exposed to air-sparged solution with a moderate [Cl−] (0.1 M) as part of the couple with the largest Cu:CS area ratio.

Monitoring and testing corrosion and responsive behaviour in galvanic systems.

Testing methods for corrosion prevention in structures have, historically, been based on the steel polarising from the protective current. Modern galvanic systems aim to protect the steel by restoring the protective alkaline environment, rather than through polarisation. Since 2012 standard guidelines allow for alternative testing to be used [1]. Scientific testing of galvanic systems will be discussed looking at the nature of constant potential galvanic systems and comparing them to the traditional constant current impressed systems, looking in particular at unique anode behaviours such as low median current during times of low corrosion risk and responsive behaviour during corrosion hazards. This work lays out a protocol for the evaluation and testing of existing galvanic corrosion protection (CP) systems in reinforced concrete through the lens of various real-world studies. Data taken from over a decade of monitored systems are used to support the protocol. Modern testing strategies such as 2-dimensional relative potential mapping and corrosion rate monitoring will measure the steel's corrosion. Galvanic currents rise and fall with corrosion risk providing protection while ensuring a long life to the design.

Effect of Electron Irradiation on Charge Transfer in 2D Gallium Monosulfide

The features of the effect of electron irradiation with an energy of 4 MeV and a dose of 2 × 1012-1013 cm−2 on the dielectric properties and AC-conductivity in alternating current of a 2D layered single GaS crystal in a frequency range of 5 × 104−3.5 × 107 Hz are established. It is shown that the electron irradiation of a single GaS crystal increases the real component of the complex dielectric constant, decreases its imaginary component, causes the dielectric loss tangent and AC-conductivity across the layers. Both before and after the electron irradiation, the conductivity varies according to a law characteristic of the hopping mechanism of charge transfer over states localized near the Fermi level. It is shown that at 140–238 K in the layered single GaS crystals across their natural layers in the constant electric field there is also a hopping conductivity (DC-conductivity) with a variable jump length along the states localized near the Fermi level. The effect of electron irradiation on the electrical conductivity of single GaS crystals and the parameters of the states localized in their forbidden gap was studied. Taking into account the experimental data obtained in alternating and direct currents the density of states near the Fermi level and their energy spread, average hopping distances in the area of activation hopping conductivity, as well as the activation energy of jumps, are estimated in both pure and electron irradiated GaS crystals.

Stray current, leakage current, alternating current, high-voltage tension, electrocorrosion, artificial constructions, protective screens

The destructive effects of the corrosive effects of stray and leakage currents are observed in almost all industries.The question is the most relevant for the railways. It is known that direct (DC) leakage currents and stray currents cause significant corrosion damage. It is supposed that corrosion from alternating current exposure is more moderate and does not cause significant damage. However, the analysis of literature data, data of theoretical, experimental and exploitative research indicates a significant destructive effect of alternating leakage current and high voltage on the structures of railway facilities in Ukraine. At the same time, measures to prevent electrocorrosion of reinforced concrete and other structures by alternating current are not provided for in the regulatory documents for railway structures. One of the reasons for this is the specificity of the processes of electro-corrosion of concrete, reinforced concrete and mortar in flooded structures.All existed methods of protection against electro-corrosion do not take into account the real mechanism of corrosion destruction of non-metallic parts of the structure. Based on this, it became necessary to develop schemes and constructive solutions for the protection of railway structures against electrocorrosion caused by alternating current, based on the fundamental principles of colloidal chemistry and physico-chemical mechanics.Developed measures and constructive solutions for the protection of concrete, reinforced concrete and stone engineering structures of railways from electrocorrosion caused by alternating high-voltage and leakage currents: solid steel screen with a deep grounding; mesh screens at the bottom of the supports with deep grounding; liquid glass screen with deep grounding. The effectiveness of the developed measures is caused by taking into account the actual mechanism of destruction of steel reinforcement and concrete structures.

Real‐time optimisation of emergency demand response and HVDC power modulation to improve short‐term frequency stability of the receiving‐end power systems

In recent years, large-capacity high-voltage direct currents (HVDCs) have been employed to transfer electricity from the west to the east of China. However, the frequent frequency drops due to HVDC blockings seriously threaten the short-term frequency stability of receiving-end power systems. The existing emergency frequency control strategy is not adaptive to the varying operation conditions and may cause excessive or deficient actions, which could result in inefficient control or high risk of frequency instability. Therefore, a real-time coordinated control strategy is proposed in this study based on the online-updated frequency response model. The model is designed to incorporate multiple types of generators and to reflect the dynamic frequency response of loads. The new control strategy combines multiple control resources, including the emergency demand response and HVDC power modulation, to improve the short-term frequency stability after HVDC failures. By online data preparation and cubic fitting, the nadir of the frequency is expressed as an analytic function of the control variables. A real-time optimisation of emergency controls is achieved to improve the short-term frequency dynamics. Case studies show that the proposed scheme is robust to the varying operation conditions and has lower control cost than the existing control strategy.

First harmonic measurements of the spin Seebeck effect

We present measurements of the spin Seebeck effect (SSE) by a technique that combines alternating currents (AC) and direct currents (DC). The method is applied to a ferrimagnetic insulator/heavy metal bilayer, Y3Fe5O12 (YIG)/Pt. Typically, SSE measurements use an AC current to produce an alternating temperature gradient and measure the voltage generated by the inverse spin-Hall effect in the heavy metal at twice the AC frequency. Here, we show that when Joule heating is associated with AC and DC bias currents, the SSE response occurs at the frequency of the AC current drive and can be larger than the second harmonic SSE response. We compare the first and second harmonic responses and show that they are consistent with the SSE. The field dependence of the voltage response is used to distinguish between the damping-like and field-like torques. This method can be used to explore nonlinear thermoelectric effects and spin dynamics induced by temperature gradients.

A facile growth control of perovskite SrTiO3 thin films by tailoring surface morphologies of TiN seeding layers in the hydrothermal-galvanic couple synthesis

Growth control of cubic perovskite structure strontium titanate (SrTiO3) thin films was facilely achieved by tailoring surface morphologies of the TiN seeding layer in the hydrothermal-galvanic couple (HT-GC) synthesis. Two types of TiN thin films with pyramidal (P-TiN) and granular (G-TiN) surface morphologies were deposited on Si substrates by sputtering. The TiN-coated Si working electrodes were then directly connected to the Pt counter electrode without applying any external power source and soaked in 0.1 M Sr(CH3COOH)2 mixed with 2 M NaOH at 80 °C for 1–60 min. Significant galvanic currents were detected during the HT-GC synthesis. Directional oriented cubic SrTiO3 thin films grew over the two types of highly preferred oriented TiN seeding layers. The growth kinetics of SrTiO3 was deduced by fitting the coverage of the oxide over the two types of TiN at different reaction times to a modified Avrami equation. It was shown that galvanic currents, relative peak integrated intensities, and growth rates of SrTiO3 over the P-TiN were much higher than those on the G-TiN, while the grain sizes of SrTiO3 over the P-TiN were smaller. The faceted surfaces with fewer phase boundaries for P-TiN could yield a different rate-limiting step during the HT-GC synthesis and enhance significantly the growth of the oxide. This facile growth control could also be applied to similar perovskite oxide/conductive nitride systems.