Passage Of Electric Current Research Articles

Experimental and Monte Carlo simulation studies on percolation behaviour of a shape memory polyurethane carbon black nanocomposite

Electro-active shape memory polymer nanocomposite from polyurethane matrix with carbon black fillers was synthesized and characterised for its electrical properties. The polyurethane matrix possesses high transition temperature, which enables it to be a candidate for high temperature applications. The carbon nanoparticle content was varied with conductivity measured at each instance, and a percolation threshold value of 6% was observed experimentally. The conductivity phenomenon was studied using Monte Carlo simulation approach on a pseudo random model of the system, developed using constrained optimization by linear approximations algorithm in visual C language platform. The probability of three dimensional network formations of carbon particles was evaluated for varying filler loading and percolation threshold of 6.2% was obtained from the model. The conductive networks formed have resulted in multiple electron paths, generating volumetric heating of the system while connected with a known power supply. This joule heating was used as stimuli for activating the shape memory behaviour by passage of electric current. High shape recovery efficiency (>95%) observed with faster recovery time (25 s), along with high transition temperature (85°) can help to qualify the system for space applications.

Electrical conductive 3D-printed monolith adsorbent for CO2 capture

Abstract The development of an adsorbent material by 3D printing technology with high CO2 adsorption capacity and electrical conductivity is presented for application in Electric Swing Adsorption process. The adsorbent is composed by zeolite 13X, activated carbon and binder. The prepared ink was characterized in order to determine its rheological properties. Two honeycomb monoliths, one with 30 × 30 × 43 mm3 and another one with 30 × 28 × 10 mm3 were printed. Textural characterization was performed by several techniques, including CO2 adsorption at 273 K. A high CO2 adsorption capacity of 3.49 mol/kg was obtained for the 3D-printed monolith at 0.15 bar and 273 K. Mechanical strength of the material was evaluated in a piece with 10 × 10 × 4 mm3. A value of 5.0 MPa was obtained. Heating of the material was tested by Joule effect through an electric current passage in the monolith, which presented a resistivity of 0.28 Ωm. An increase of temperature of about 80 K was achieved in 180 s, with a power consumption of 3.25 W. An adsorption quantity of CO2 of 1.45 mol/kg (at 0.09 bar and 303 K) was obtained by adsorption equilibrium isotherms measurements. These experiments demonstrated that the printed material is suitable for Electric Swing Adsorption processes applied for CO2 capture.

Detecting heart tissue injury in electrocution human cases using heart-type fatty acid-binding protein 3

Introduction: In the medicolegal daily practice, electrocution is a traumatic cause of death owing to wide use of electricity and electrical devices in different activities of modern life at home and workplaces. Electrical current passage through tissues elaborates different types of energy (the electrical, thermal, and mechanical energies) which can cause skin lesions, multiorgan damage, and even death. The severity and extent of tissue injuries depend on the current type (alternating current [AC] or direct current), its strength (amperage), voltage (low or high), frequency, tissue resistance, duration of exposure, and its pathway through the body. Microscopic examination of tissue samples from the heart may show nonspecific findings to electrocution, but sometimes none is detected by conventional hematoxylin and eosin stains (H and E). Therefore, immunohistochemical studies could help the forensic pathologists in their diagnosis, especially cases with less typical findings or obscure circumstances. Heart-type fatty acid-binding protein 3 (H-FABP3) is a small cytoplasmic protein of (15 kDa), composes of 133 amino acids, involves in active fatty acid metabolism, and transports fatty acids from the cell membrane to mitochondria for oxidation. Due to its cytoplasmic location and small molecular weight, it released from cardiac myocytes into the circulation following an ischemic episode. Objective: This study was conducted to evaluate the effect of electric current on the expression of H-FABP3 in human heart tissue autopsy samples. Methods: Human heart tissue samples were collected during the period from January 1 2016 to June 30, 2016, through autopsy of 30 medicolegal cases of electrocution as well as 30 cases of fatal head injuries which were used as control. They were examined by conventional histopathological H and E stain and immunohistochemical technique so that H-FABP3 was detected using FABP3 polyclonal antibody and demonstrated by ready to use biotin-free, one-step horseradish peroxidase polymer anti-mouse, rat, and rabbit immunoglobulin G with 3,3'-diaminobenzidine to achieve the aim of this study. Results: This study shows that electric shock was the fifth cause of traumatic death, being responsible for death of only 4.5% of cases referred to the medicolegal directorate in Baghdad during the period of study. It is almost accidental death in Iraqi society with higher incidence to be due to contact with low-voltage household AC sources with young males at the age of (15–20 years old) are being more vulnerable to fatal electrical injury than females during their early productive life (with male:female ratio = 6:1). Heart tissue ischemia is a major cause of death following electrocution, especially when victim being in contact with household low-voltage AC in the presence of transthoracic pathway to the ground and low body resistance due to skin wet which can cause death within a minute in association with mild if any electrical skin burns. Electrocution has a significant effect on H-FABP3 stain total index as it causes depletion of FABP3 total stain index with mean of 0.28 ± 0.149177SD for tissue sections of the heart muscle in the affected areas of human cases. Conclusions: Immunohistochemical heart tissue samples' examination which shows dramatic depletion in H-FABP3 total stain index in affected area(s) is of value in detecting heart tissue injury caused by electrocution during the early period after death even in the absence of grossly and microscopically visible lesion(s).

Improved electrical stability of silver NWs based hybrid transparent electrode interconnected with polymer functionalized CNTs

Silver nanowires have high potential to replace the conventional transparent conductors in many applications. However, the electrical instability of silver nanowires especially when heated as a result of electrical current passage causes the failure of this type of conductors and thus may limit their uses in many applications. In this study, a novel approach based on interconnecting the individual nanowires with conductive polymer wrapped carbon nanotubes is examined to improve the stability of silver nanowires network. The hybrid electrode with modified carbon nanotubes shows highly stable electrical performance in comparison to silver nanowires electrode. Under continuous electrical stress, slight variation in the sheet resistance of the hybrid electrode was noticed and was about two order of magnitude less than that of silver nanowires electrode. Moreover, the thermal studies reveal that the hybrid electrode stabilizes at much lower temperature than that of silver nanowires electrode. The findings show that the proposed approach is very promising to overcome the failure issue of silver nanowires and to increase the feasibility of their use for device applications.

On the applicability of the electrodynamic approximation in the simulation of the electrovortex flow in the presence of an external magnetic field

Experimental and numerical results on the effect of an external axial magnetic field on the structure of the flow which occurs when an electric current passes through a conducting medium between two hemispheres are presented. Results show that for high external axial magnetic field it is absolutely necessary to take into account the induced currents generated by the flow. These results can be used in electrometallurgy for a priori estimates of the flow structure in the direct-current-arc furnaces.

Experimental and numerical investigation of the instability of the electrovortex flow in hemispherical container

Experimental and numerical results on the effect of an external vertical magnetic field (MF) on the structure of the flow which occurs when an electric current passes through a conducting medium between two hemispheres are presented. The experiments on the velocity measurement were carried out on the eutectic alloy In–Ga–Sn with the unique fiber-optic transducers. The fiber-optic technique for measuring velocity is described. Results on influence of the axial external MF on the flow are presented. The boundary curve separating the one-vortex and two-vortices flow modes depending on the current values through the experimental setup and the external MF was obtained. These results can be used in electrometallurgy for a priori estimates of the flow structure in the direct-current-arc furnaces.

Electromechanical systems based on polymer hydrogels for micro-scale actuators

The paper proposes a novel approach to the construction of actuators for automation and robotics based on the use of new electroactive polymer materials – swelling hydrogels. The hydrogel pH-sensitive materials containing two polymer components, crosslinked polyacrylic acid and polyvinyl alcohol, are obtained. A procedure for the synthesis of hybrid hydrogel is described, and the achieved values of their characteristics, degrees of swelling in water and water solution of salt, are given. A method of hydrogel elements preparation with a specified geometric configuration was developed, and cylindrical and also ring-shaped samples were prepared. Mechanical properties of the prepared hydrogels at compression were measured. It is shown that the hybrid hydrogels exhibit higher strength and elasticity than the one-component polyacrylic acid hydrogels obtained by the same method. An actuator design is proposed with a hydrogel as a controlled element. An experimental layout of such actuator was constructed. The stability of material characteristics was determined, and methods for the electrodes fixation and electric current supply were developed. It was found that ring-shaped samples of hydrogels demonstrate electromechanical response – compression when electric current passes through their cross section. This fact was the evidence that these hydrogels can be used as a linearly operating generator of mechanical force. It is shown that this effect is more pronounced for samples swollen in water solution of sodium sulfate rather than in distilled water.

Inactivation of Microorganisms in Foods by Ohmic Heating: A Review

Ohmic heating (OH) is an alternative food processing technology for effectively inactivating microorganisms that depends on the heat that has been generated when electrical current passes directly through food material. The advantages of OH for microbial inactivation include shorter heating time, more uniform heat distribution inside food, reduced nutrition losses, and higher energy efficiency. This review presents some published information regarding the inactivation of microorganisms by OH, including the major factors that influence the inactivation effectiveness of OH, the inactivation of vegetative cells and spores in foods by OH, the inactivation mechanisms of OH, and the challenges and prospects of OH for food processing. This information will improve the understanding of OH for inactivation of microorganisms and promote the application of OH in the food industry.

Exotic grain growth law in twinned boron carbide under electric fields

Grain growth is a ubiquitous phenomenon in all materials, and it affects both structural and functional properties. Despite its intrinsic importance, a full comprehension of grain growth from a fundamental point of view—i.e., from the nanoscale to the macroscale—is still a pending issue. In practical terms, our knowledge relies on the classical kinetic laws reported sixty years ago.This paper reports the violation of such classical laws in boron carbide ceramics consolidated by spark plasma sintering. The conjunction of high temperature gradients with large compressive stress when a pulse electric current passes through the ceramic powders gives rise to an intense twinning–detwinning formation. These forming steps at the grain boundaries change the grain mobility drastically. Therefore, a new ‘exotic’ law for grain-growth kinetics is found and validated at different temperatures and dwell times.

Elements of non-destructive damage monitoring by electrostatic potential method

We establish a correlation between the magnitude of a propagating crack in current-carrying flat samples and the change in the electric potential field over the surface of the sample when an electric current passes through it. The experimental data correspond to an analytic solution obtained using a conformal map in the two-dimensional formulation. This work can be related to the area of converting mechanical quantities into electrical quantities, which simplifies the process of recording mechanical processes and provides a convenient form for controlling and managing them. This work is aimed at the automatic control of the process of the destruction of conductive materials.

СОЕДИНЕНИЕ АВТОМОБИЛЬНЫХ ПРОВОДНИКОВ МЕТОДОМ УЛЬТРАЗВУКОВОЙ СВАРКИ. ПОЖАРНАЯ ОПАСНОСТЬ

Introduction. Nowadays ultrasonic welding of metals including conductors is widely used. The con­nection of copper conductors by ultrasound is based on high-frequency oscillations. Materials and methods. Copper stranded conductors interconnected by ultrasonic welding were chosen as the materials for the study. The study of these samples was carried out in the laboratory by metallographic analysis. Results and discussion. In case of a poor contact at the connection point, a large transient resistance may occur when an electric current passes through a given point and cause fire. To establish the involvement of a poor adhesion to the occurrence of a fire, it is necessary to conduct metallographic studies of the compound. With qualitatively performed welding, fusion of individual sections of wires at the junction site is observed, while in the case of a “poor” connection, clearly defined boundaries are observed. A very long exposure to ultrasound in the welding process on the connected conductors leads to a de­crease in the plasticity of the conductor, which in turn leads to the fracture of the veins near the junction and, as a consequence, to the emergence of local current overload. Where the places of rupture after the fire are melted and smoked, indicates that the test conductor was damaged even before the ignition of the vehicle. Conclusion. Thus, the possibility of vehicle combustion as a result of a poorly executed connection of conductors by ultrasonic welding is shown. It is noted that the fire can be caused by uncompleted welding (“non-fusion” of the conductors), or vice versa when an impact of ultrasonic waves on the conductors to be connected has been too long. It is necessary to withdraw this connection directly at the seat of fire for further laboratory metallo­graphic research.

КИНЕТИКА РАЗДЕЛЕНИЯ СЛОЖНЫХ РАСТВОРОВ ХРОМАТИРОВАНИЯ

Research into the kinetics of processes associated with the regeneration of spent chromium-containing solutions primarily aims to determine such basic parameters, as the order and rate constants of the reactions involved, their activation energies and transference numbers. All these parameters determine the efficiency of the regeneration process and its power consumption values. In addition, knowledge of these dependencies is essential for the selection of optimal operating modes of a device for regenerating spent chromium-containing solutions, as well as for the development of mathematical models and engineering calculation methods describing such processes. On the basis of experimental data, a functional relationship between changes in the values of electric current intensity and transference numbers has been established. The optical density of samples was measured using a photoelectric concentration colorimeter KFK-2-UHL 4.2. The voltage and current intensity values were controlled and regulated using a power supply unit Mastech HY3005-2. It is shown that an increase in the intensity of electric current leads to a decrease in the mobility of chromium ions. This occurs because the gas is absorbed by the solution, which prevents the passage of electric cur-rent. In addition, an increase in the current intensity results in the deposition of chromium on the electrode. Optimal dependencies between the key kinetic characteristics and parameters of the re-generation process are provided. Diagrams are presented for calculating optimal parameters of the process and corresponding power consumption values, which can be helpful in carrying out the re-generation of spent chromium-containing solutions with a high efficiency.

Liquid Metal‐Conductive Thermoplastic Elastomer Integration for Low‐Voltage Stiffness Tuning

AbstractAn electrically responsive composite is introduced that exhibits muscle‐like changes in elastic stiffness (≈1–10 MPa) when stimulated with moderate voltages (5–20 V). The stiffness‐tuning element contains an embedded layer of conductive thermoplastic elastomer (cTPE), composed of a propylene–ethylene copolymer and a percolating network of carbon black. Two opposite surfaces of the cTPE layer are coated with a ≈20 µm thin film eutectic gallium–indium (EGaIn) liquid metal alloy. When a voltage is applied to these EGaIn electrodes, electric current passes through the cTPE. This causes internal Joule heating, which induces a phase transition that changes the composite from its stiff state (E = 10.4 MPa) to its compliant state (E = 0.7 MPa). Differential scanning calorimetry is performed to show that this state change is governed by a solid–liquid transition. Voltage‐dependent activation times are demonstrated that can be reduced to below 2 s and show the ability of the composite to recover its original shape after large strains. To illustrate its applicability in robotics, the composite is incorporated into an underactuated robotic finger, providing it with two different bending modes. The ability to use the composite as a moldable stiffness‐tuning splint is also demonstrated.

Periodontal pathogens promote epithelial-mesenchymal transition in oral squamous carcinoma cells in vitro

ABSTRACTEpithelial-mesenchymal transition (EMT) is potentially involved in increasing metastasis of oral squamous cell carcinoma (OSCC). Periodontal pathogens are well-known for their ability to induce intense immune responses and here we investigated whether they are involved in inducing EMT. Cultures of OSCC cell line (H400) were treated separately with heat-killed periodontal pathogens F. nucleatum, or P. gingivalis or E. coli LPS for 8 d. EMT-associated features were assayed using sq-PCR and PCR-arrays, for EMT-related markers, and ELISAs for TGF-β1, TNF-α, and EGF. The migratory ability of cells was investigated using scratch and transwell migration assays. E-cadherin and vimentin expression was assessed using immunofluorescence while Snail activation was detected with immunocytochemistry. In addition, the integrity of the cultured epithelial layer was investigated using transepithelial electrical resistance (TEER). PCR data showed significant upregulation after 1, 5, and 8 d in transcription of mesenchymal markers and downregulation of epithelial ones compared with unstimulated controls, which were confirmed by immunofluorescence. Periodontal pathogens also caused a significant increase in level of all cytokines investigated which could be involved in EMT-induction and Snail activation. Exposure of cells to the bacteria increased migration and the rate of wound closure. Downregulation of epithelial markers also resulted in a significant decrease in impedance resistance of cell monolayers to passage of electrical current. These results suggested that EMT was likely induced in OSCC cells in response to stimulation by periodontal pathogens.

Influence of the external magnetic field on hydrodynamic structure of the electrovortex flow in hemispherical container

Experimental and numerical results on the effect of an external vertical magnetic field on the structure of the flow which occurs when an electric current passes through a conducting medium between two hemispheres are presented. The experiments on the velocity measurement were carried out on the eutectic alloy In-Ga-Sn with the unique fiber-optic transducers. Results on influence of the axial external magnetic field on the flow are presented. The boundary curve separating the one-vortex and two-vortices flow mode depending on the current values through the experimental setup and the external magnetic field was obtained. These results can be used in electrometallurgy for a priori estimates of the flow structure in the direct-current-arc furnaces.

Continuous ohmic heating system for the pasteurization of fermented red pepper paste

Abstract Ohmic heating (OH) is a processing in which heat is generated inside foods by the passage of electric current. This study aimed to determine the optimal conditions for pasteurizing the Gochujang Korean-style fermented food containing hot pepper paste using a continuous OH system. The effective conditions for OH involved three pairs of electrodes connected diagonally and excitation over the voltage range of 50–100 V. The selected conditions provided heating above 100 °C without scale buildup. A microbial inactivation with a 2 log reduction was achieved by the OH, with the processing time being shorter than for conventional heating (CH). OH was available for 57 cycles during 1 cycle of CH, and it could process 104.4 kilotonnes of product. The consistency index related to thickening properties was markedly higher for OH than for CH. This study has confirmed that continuous OH is suitable for the heat-based sterilization of highly viscous foods. Industrial relevance Ohmic heating (OH) is a food processing technique in which heat is generated inside food products by the passage of alternating electric current. This study aimed to determine the optimal conditions for pasteurizing the Gochujang Korean-style fermented food containing hot pepper paste using a self-designed continuous OH system. The effective conditions for OH involved three pairs of electrodes connected diagonally and excitation over the voltage range of 50–100 V. The selected conditions provided heating above 100 °C without scale buildup. The rapid and uniform OH produced a microbial inactivation effect of a 2 log reduction despite the shorter processing time than for batch-type conventional heating (CH). OH was available for 57 cycles during 1 cycle of CH, and it could process 104.4 kilotonnes of food products. And the continuous OH is suitable for the heat-based sterilization of highly viscous foods and could result in better energy efficiency and be suitable for implementation in industrial applications.

Directed motion of vortices and annihilation of vortex–antivortex pairs in finite-gap superconductors via hot-lattice routes

Using finite gap, time-dependent Ginzburg–Landau equations, generalized to include non-thermal phonons, we report numerical simulations of vortex nucleation, propagation, and annihilation in thin, finite strips of magnetic-impurity free, perfectly homogeneous superconductors. When a steady electric current passes through the strip with either surface defects or nonequilibrium phonon sources (e.g., local “hotspots”), periodic vortex generation and annihilation is observed even in the absence of external magnetic fields. Local pulses of electric field are produced upon annihilation. The injected phonon lines steer the vortices during their motion within the strip, potentially allowing control of the annihilation site.

Measurement of Non-Effective Electric Current in Electrodialysis Stacks

The driving force of electrodialysis is applied voltage and electric current. In the event that the module is composed of a number of mutually hydraulically connected subunits (membrane pairs), electric current passes through a part outside the active part along peripherals providing the supply of raw materials. This work focuses on the measurement of these currents that are lost inefficiently. The influence of module geometry on electrodialysis, conductivity of working solutions and applied voltage were studied. The influence of the presence of an ion-conductive membrane in the sealing area on the performance of a membrane stack has been proven. A relation between the conductivity of a membrane and the conductivity of electrolytes to the amount of leakage currents has been found. On the contrary, voltage applied does not primarily influence the distribution of leakage currents but it affects the degree of desalination and the conductivity of solutions in collecting and feeding channels. In the pilot and operating modules with 25 and 50 membrane pairs that were used, the calculated leakage current reaches 0.2–1.2% of the total current load depending on the design and operating conditions.

Study on high-voltage conductivity provided solely by field-enhanced dissociation in liquid dielectrics

The study investigates the process of the electrical current passage in a system with non-uniform electric field under assured absence of injection. The cell has a special design, with the region of the strong electric field located far from metal electrode surfaces and the non-linearity of the current-voltage characteristics ensured solely by the field-enhanced dissociation. The characteristics were measured experimentally and studied numerically for dielectric liquids with different values of low-voltage conductivity; the results were compared. The computations were carried out on the basis of the complete set of electrohydrodynamic equations using commercial software package COMSOL Multiphysics.

Computational Modeling of Arc–Slag Interaction in DC Furnaces

The plasma arc is central to the operation of the direct-current arc furnace, a unit operation commonly used in high-temperature processing of both primary ores and recycled metals. The arc is a high-velocity, high-temperature jet of ionized gas created and sustained by interactions among the thermal, momentum, and electromagnetic fields resulting from the passage of electric current. In addition to being the primary source of thermal energy, the arc jet also couples mechanically with the bath of molten process material within the furnace, causing substantial splashing and stirring in the region in which it impinges. The arc’s interaction with the molten bath inside the furnace is studied through use of a multiphase, multiphysics computational magnetohydrodynamic model developed in the OpenFOAM® framework. Results from the computational solver are compared with empirical correlations that account for arc–slag interaction effects.