Direction Of Current Flow Research Articles

High-Q On-Chip Capacitors Featuring “Self-Inductance Cancellation” for RF and mm-Wave Applications

In this letter, we are reporting on the characterization of the on-chip metal–oxide–metal (MOM) capacitors that use “self-inductance cancellation” technique resulting in high-performance operation in radio frequency (RF)/millimeter-wave (mm-wave) regime. The utilized method helps mitigate the mutual magnetic induction between the metal fingers of a MOM capacitor while they are placed in proximity to each other, by controlling the direction of the RF current flow. More than two times inductance cancellation is achieved, thus resulting in an increase of the self-resonance frequency and quality factor ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> -factor) of the RF capacitor. The test structures are fabricated using Intel 16 FinFET technology, where postsilicon data show a good agreement between the theory and simulation. This methodology is CMOS compatible and is applicable to RF/mm-wave circuits that employ RF capacitors toward improving the RF system performance.

(Digital Presentation) Finite Element Modeling of Thermoelectric Effects in Phase Change Memory Cells

We model the current density in a semiconductor based on the drift-diffusion transport of the charge carriers to accurately determine the thermoelectric effects in the bulk material (Thomson effect) and material junctions (Peltier effect). We utilize the model to perform 2-D finite element simulations of mushroom phase change memory cell with a critical dimension of 20 nm using temperature and electric field dependent material parameters and analyze the contributions of symmetric Joule heating and asymmetric thermoelectric heats during reset and set operations. We investigate the effect of altering the direction of current flow by changing the connection point between the cell and the access device and observe that, corresponding change in thermoelectric effects cause significant difference in operation dynamics, temperature distribution profiles, amorphous volume, energy requirement and resistance contrast between reset and set states.

Effects of theta transcranial alternating current stimulation (tACS) on exploration and exploitation during uncertain decision-making

Exploring ones surroundings may yield unexpected rewards, but is associated with uncertainty and risk. Alternatively, exploitation of certain outcomes is related to low risk, yet potentially better outcomes remain unexamined. As such, risk-taking behavior depends on perceived uncertainty and a trade-off between exploration-exploitation. Previously, it has been suggested that risk-taking may relate to theta activity in the prefrontal cortex. Furthermore, previous studies hinted at a relationship between a right-hemispheric bias in frontal theta asymmetry and risky behavior. In the present double-blind sham-controlled within-subject study, we applied bifrontal transcranial alternating current stimulation (tACS) at the theta frequency (5 Hz) on eighteen healthy volunteers during a gambling task. Two tACS montages with either left-right or posterior-anterior current flow were employed at an intensity of 1 mA. Results showed that, compared to sham, theta tACS increased perceived uncertainty irrespective of current flow direction. Despite this observation, no direct effect of tACS on exploration behavior and general risk-taking was observed. Furthermore, frontal theta asymmetry was more right-hemispherically biased after posterior-anterior tACS, compared to sham. Finally, we used electric field simulation to identify which regions were targeted by the tACS montages as an overlap in regions may explain why the two montages resulted in comparable outcomes. Our findings provide a first step towards understanding the relationship between frontal theta oscillations and different features of risk-taking.

Design and Fabrication of Thermoelectric Air-Cooling System

A thermoelectric air-cooling system (TEACS) is an innovative technology based on the thermoelectric cooling phenomenon. The absence of heavy moving parts to obtain a cooling effect reduces intense vibrations than the traditional cooling system. Moreover, this system is eco-friendly as harmful coolants are not used or produce any harmful elements such as CFCs. The thermoelectric module works on direct current (DC), heating & cooling phenomena depending upon the direction of current flow. Peltier modules are made up of two unique semiconductor materials, such as Bismuth Telluride (Bi2Te3) in the form of pillars sandwiched between a pair of ceramic plates. This paper covers the design and fabrication of an automated thermoelectric air-cooling system. The Peltier module is sandwiched between two Aluminum heatsinks on each side of the Peltier module. Arduino microcontroller is used to provide automatic temperature control. Air is passed through the cold side, and water is used to reduce the heat on the hot side. This system reached 25°C within 300 seconds and 700 seconds to reach 15°C from 30°C ambient room temperature. The novelty of this TEACS has a COP of 1.13 achieved by careful adjustment of electrical parameters with a cooling capacity of 648 W, and the designs are fabricated by using eco-friendly materials.

Observation of ballistic upstream modes at fractional quantum Hall edges of graphene

The presence of “upstream” modes, moving against the direction of charge current flow in the fractional quantum Hall (FQH) phases, is critical for the emergence of renormalized modes with exotic quantum statistics. Detection of excess noise at the edge is a smoking gun for the presence of upstream modes. Here, we report noise measurements at the edges of FQH states realized in dual graphite-gated bilayer graphene devices. A noiseless dc current is injected at one of the edge contacts, and the noise generated at contacts at length, L = 4 μm and 10 μm away along the upstream direction is studied. For integer and particle-like FQH states, no detectable noise is measured. By contrast, for “hole-conjugate” FQH states, we detect a strong noise proportional to the injected current, unambiguously proving the existence of upstream modes. The noise magnitude remains independent of length, which matches our theoretical analysis demonstrating the ballistic nature of upstream energy transport, quite distinct from the diffusive propagation reported earlier in GaAs-based systems.

Highly Oriented Carbon Nanotube Supercapacitors

The demand for supercapacitors (SCs) with high capacitance, high charge–discharge rate, and long lifespan has been increasing because of the rapid development of wearable devices. In particular, flexible and durable SCs are essential for applications in wearable devices. A reasonable strategy to achieve such SCs involves the design and fabrication of SCs with flexible materials. In this study, we present a flexible SC with highly oriented carbon nanotube (CNT) sheets, which exhibit all the component functions of SCs: activated materials, conductive materials, and current collectors. Repeated bending tests validated the robustness of the flexible SCs. The SCs demonstrated extremely high durability with >99.9% capacitance retention after 50 000 bending cycles. Furthermore, we observed that the orientation angle of the CNT sheets with respect to the current flow direction (θ) was crucial for determining the performance of SCs. The SCs with CNT sheets oriented in the current flow direction (θ = 0°) showed a higher scan rate and robustness than those with other CNT sheet orientations (θ = 45 or 90°), because of the ease of access of charge carriers to the electrodes of the entire CNT sheet. Well-designed flexible and durable CNT-SCs can drastically improve the performance of future flexible devices.

A New Hybrid Cascaded Switched-Capacitor Reduced Switch Multilevel Inverter for Renewable Sources and Domestic Loads

This multilevel inverter type summarizes an output voltage of medium voltage based on a series connection of power cells employing standard configurations of low-voltage components. The main problems of cascaded switched-capacitor multilevel inverters (CSCMLIs) are the harmful reverse flowing current of inductive loads, the large number of switches, and the surge current of the capacitors. As the number of switches increases, the reliability of the inverter decreases. To address these issues, a new CSCMLI is proposed using two modules containing asymmetric DC sources to generate 13 levels. The main novelty of the proposed configuration is the reduction of the number of switches while increasing the maximum output voltage. Despite the many similarities, the presented topology differs from similar topologies. Compared to similar structures, the direction of some switches is reversed, leading to a change in the direction of current flow. By incorporating the lowest number of semiconductors, it was demonstrated that the proposed inverter has the lowest cost function among similar inverters. The role of switched-capacitor inrush current in the selection of switch, diode, and DC source for inverter operation in medium and high voltage applications is presented. The inverter performance to supply the inductive loads is clarified. Comparison of the simulation and experimental results validates the effectiveness of the proposed inverter topology, showing promising potentials in photovoltaic, buildings, and domestic applications. A video demonstrating the experimental test, and all manufacturing data are attached.

Comparative Study of 10-MW High-Temperature Superconductor Wind Generator with Overlapped Field Coil Arrangement

The electromagnetic characteristics and iron loss of a high-temperature superconductor wind generator (HWG) equipped with an overlapped field coil arrangement (OFCA) are studied by comparing with the one equipped with the conventional field coil arrangement (CFCA). Through a quantitative analysis, it was found that HWG with OFCA exhibits better electromagnetic characteristics than HWG with CFCA and can reduce the iron loss by eliminating the magnetic flux sag caused by the adjacent field coil sides with the same current flow direction. In addition, the OFCA topology can further reduce the volume of the wind generator.

THE INFLUENCE OF THE COASTAL CURRENT ON THE ESTIMATION OF RELATIVE ABUNDANCE INDICES IN SMALL-SCALE SHRIMP FISHERY

The aim of this scientific note was to evaluate the influence of the coastal current on the estimation of relative abundance indices for small-scale marine shrimp trawling to indicate the best relative abundance index to be used for stock assessment and conservation. Georeferenced experimental trawls were carried out with standardized equipment and capture time on the coast of Rio Grande do Norte, northeastern Brazil. Drags followed convergent and divergent orientations in relation to the flow of the local coastal current. The results showed that the direction of the coastal current flow directly influences the distances and drag shifts, generating variations in the sampling effort and, consequently, bias when using Catch per Unit Effort (CPUE) as a relative abundance index. Conversely, the adoption of Catch per Unit of Swept Area (CPUA) as an index of relative abundance for shrimp trawling becomes more suitable since the variations in the distances of trawl shifts are perceptible through this index.

Electrode montage-dependent intracranial variability in electric fields induced by cerebellar transcranial direct current stimulation

Transcranial direct current stimulation (tDCS) is an increasingly popular tool to investigate the involvement of the cerebellum in a variety of brain functions and pathologies. However, heterogeneity and small effect sizes remain a common issue. One potential cause may be interindividual variability of the electric fields induced by tDCS. Here, we compared electric field distributions and directions between two conventionally used electrode montages (i.e., one placing the return electrode over the ipsilateral buccinator muscle and one placing the return electrode [25 and 35 cm2 surface area, respectively] over the contralateral supraorbital area; Experiment 1) and six alternative montages (electrode size: 9 cm2; Experiment 2) targeting the right posterior cerebellar hemisphere at 2 mA. Interindividual and montage differences in the achieved maximum field strength, focality, and direction of current flow were evaluated in 20 head models and the effects of individual differences in scalp–cortex distance were examined. Results showed that while maximum field strength was comparable for all montages, focality was substantially improved for the alternative montages over inferior occipital positions. Our findings suggest that compared to several conventional montages extracerebellar electric fields are significantly reduced by placing smaller electrodes in closer vicinity of the targeted area.

Mechanism of Rip Current Generation at Deoksan Beach, South Korea

Chang, S.-Y.; Kim, J.-H.; Lee, H.-S., and Kim, I., 2021. Mechanism of rip current generation at Deoksan Beach, South Korea. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 295–299. Coconut Creek (Florida), ISSN 0749-0208. The coast serves as a buffer by reducing the energy of high waves and also serves as a leisure space for people. The east coast of Gangwon has become popular for its beach and for surfing in summer. Most beaches are sandy, and they have well-developed crescentic bars owing to exposure to high waves. The study site, Deoksan Beach, had an accident in which two college students drowned owing to rip currents at around 5:40 pm on July 13, 2019. The flow velocity and direction of the rip currents were identified using CCTV images at the time of the accident, and the causes of the currents were analyzed using data obtained from five water depths surveys conducted in 2017. At the time of the accident, the significant wave height was 0.6 m, the period was ∼7.5 s, and the wave direction was 54°. The survey results indicated that an environment suitable for rip current generation existed at this site. A numerical model experiment was conducted using the non-hydrostatic Surface Waves till Shore (SWASH) model to reproduce the occurrence of rip currents at the time of the accident, and the flow (surface: 0.38 m/s, average: 0.3 m/s) was found to be on the offshore side of the accident.

Laboratory facility development for studying the heavy charge and discharge modes effect on the degradation of lithium-ion batteries

The article is devoted to the laboratory facility development for studying the lithium-ion batteries (LIB) characteristics in severe operating conditions, typical of electric vehicles. The electrical schemes of charging and discharging modules for 18650 batteries are shown. A feature of the modules is the ability to set any form of current (change the amplitude and frequency of the signal, change the average value, change the direction of current flow). The operating principle of the control program is described, which allows independent testing of three batteries using a single microcontroller. A feature of the modules is the ability to set any form of current (change the amplitude and frequency of the signal, change the average value, change the direction of current flow). The operating principle of the control program is described, which allows independent testing of three batteries using a single microcontroller. The created laboratory facility is presented, which provides the possibility of simultaneous testing of up to 30 batteries with different test programs. An example of the laboratory facility operation in the form of a current, voltage and temperature oscillogram fragment of the experiments is given.

Investigating thermoelectric properties in conjugated polymer polyl thin films to achieve higher levels of performance

Achieving high levels of conductivity by aligning polymer chains in the direction of current flow and using a stable doping method.

Analysis of Electromagnetic Properties of Bulk Superconductors.

In the present study, a YBa₂Cu₃O7-y bulk superconductor added with 5~10 wt% Ag was fabricated employing Sm123 as a seed to produce a superconductive single crystal. Metallic silver was added to the single crystal of YBa₂Cu₃O7-y to remove defects such as cracks and pores. Electromagnetic properties of the bulk superconductor at 77 K were analyzed based on relationships of magnetic levitation, trapped magnetic force, and critical current density. The critical current density of the superconductor at 77 K and 0 T was 3.53 × 10⁴ A/cm². Discontinuous points in the distribution of magnetic field lines were not observed, implying that these two specimens grew well as a single crystal without specific weak links. For the growth of a superconductive nano crystal employing slow cooling at temperature of formation of 123 phase, superconductive nano crystals were aligned in a-b direction, the direction of peak current flow. The peak value of the trapped magnetic force of the YBa₂Cu₃O7-y superconductor specimen was 3.23 kG. Using the FC method, peak forces of attraction and repulsion were 21.696 N and 70.168 N, respectively.

Structure and 3-D Model of a Solid State Thin-Film Magnetic Sensor

Vector 3-D magnetic sensors form the basis of measurement devices for magnetic field mapping and magnetic tracking. Typically, such sensors utilize specific constructions based on split Hall structures (SHS). An SHS-based 3-D magnetic sensor is a bulk semiconductor integrated structure with 8 or more contacts. Combining current flow directions through the contacts and measuring the corresponding voltages, one defines projections BX, BY, BZ of the magnetic field vector. This work presents a novel design of 3-D solid state magnetic sensors that requires no insulation by p-n junctions and can be implemented by thin-film technology traditionally used for fabrication of Hall sensors including those based on InSb films. Besides, a SPICE model of the 3-D magnetic sensor is provided, which helps design the proposed sensor and refine techniques of its calibration.

Influence of Flow Field Design on Zinc Deposition and Performance in a Zinc-Iodide Flow Battery.

Among the aqueous redox flow battery systems, redox chemistries using a zinc negative electrode have a relatively high energy density, but the potential of achieving high power density and long cycle life is hindered by dendrite growth at the anode. In this study, a new cell design with a narrow gap between electrode and membrane was applied in a zinc-iodide flow battery. In this design, some of the electrolyte flows over the electrode surface and a fraction of the flow passes through the porous felt electrode in the direction of current flow. The flow battery was tested under constant current density over 40 cycles, and the efficiency, discharge energy density, and power density of the battery were significantly improved compared to conventional flow field designs. The power density obtained in this study is one of the highest power densities reported for the zinc-iodide battery. The morphology of the zinc deposition was studied using scanning electron microscopy and optical profilometry. It was found that the flow through the electrode led to a thinner zinc deposit with lower roughness on the surface of the electrode, in comparison to the case where there was no flow through the electrode. In addition, inhibition of dendrite formation enabled operation at a higher range of current density. Ex situ tomographic measurements were used to image the zinc deposited on the surface and inside the porous felt. Volume rendering of graphite felt from X-ray computed tomography images showed that in the presence of flow through the electrode, more zinc deposition occurred inside the porous felt, resulting in a compact and thinner surface deposit, which may enable higher battery capacity and improved performance.

Research on the Blade Motion of a Bidirectional Energy-Generating Turbine under Integrated Wave and Tidal Current Action

An integrated wave-tidal current power turbine is affected by both wave and tidal current forces, and its energy efficiency is closely related to the velocity and direction of the two forces. To improve the probability of the horizontal axis turbine reaching maximum energy efficiency under real-time changing sea conditions, we performed the following investigations in this study. Based on the actual application scenario of Lianyungang port, a time series prediction model of tidal current (velocity and flow direction) and wave (mean wave direction, mean wave period, and significant wave height) data for the past year was established. The changes in waves and tidal currents within 24 h after the cutoff point of the existing data were predicted. The integrated wave-tidal current mechanism was studied, and the superposition of wave energy and tidal current energy was transformed into the equivalent velocity vector of wave-tidal current integration. The conversion coefficient between waves and equivalent flows was determined by a numerical wave flume simulation. According to the historical wave and tidal current data, the equivalent velocity range of the integrated action of waves and tidal currents in Lianyungang was determined. The influence of different blade motions on the energy harvesting efficiency of the turbine under the corresponding flow conditions was studied using the Computational Fluid Dynamics (CFD) method to determine the blade motion law of the turbine. The blade motion law of the prototype was verified in a sea trial experiment. The experimental results were basically consistent with the simulation results for the blade motion law designed according to the wave and tidal current prediction law. This design scheme can provide a reference for engineering design for the development and utilization of new marine energy.

High-speed inspection of delamination defects in unidirectional CFRP by non-contact eddy current testing

The anisotropic bulk conductivity of carbon fibre reinforced polymers is a challenge for eddy current testing (ECT). The conductivity is markedly higher in longitudinal fibre direction compared to the transverse directions. This means that ECT has mainly been used for detecting imperfections that affect the direction and magnitude of the longitudinal conductivity. That is, fibre misalignment and broken fibres respectively. Damage in the matrix, such as delamination, affects the already low transverse bulk conductivity and is therefore very difficult to detect using ECT.A customized eddy current probe developed for detecting delamination damage in carbon fibre reinforced polymer (CFRP) composite at 4 m/s is presented in this paper. The design of the probe is based on numerical simulation of eddy current flow in the anisotropic CFRP composite. It was found that the optimal coil configuration has a current flow parallel to the conducting carbon fibres, but in two in-line coils with opposite current flow direction operating at 1 MHz frequency. This forces the eddy currents between the probes to flow perpendicular to the fibres, making the probe sensitive to changes in transverse conductivity caused by delamination. The simulated probe configuration was validated experimentally, and the constructed inspection device was able to detect real delamination damage in a CFRP component with demand for high-quality inspection.

P 23. Individualized I-waves adapted TMS – Preliminary results

Introduction. Synaptic plasticity is considered the neurophysiological correlate of learning processes in the human brain. It can be studied through transcranial magnetic stimulation (TMS). A TMS over the primary motor cortex (M1) generates descending volleys, so called I-waves (I1-I3). Their latencies can be detected with “short interval intracortical facilitation” (SICF). These latencies seem to play a pivotal role in the induction of synaptic plasticity. A paired pulse TMS, based on the defined (1.5 ms), as well as on the individual I-waves, lead to an increase in corticospinal excitability. The aim of this study was to investigate the effects of an individualized quadri-pulse theta burst stimulation (i-qTBS) with 4 bursts, based on each of the individual I1-I3- waves latencies for the first time. Methods. We studied the individual I-wave latencies through SICF in posterior-anterior (PA) and anterior-posterior (AP) current flow direction in the human M1-HAND of 12 healthy subjects (23-34 years, f=8). We used a newly engineered stimulator (MSB, Munich) to apply paired pulses with interstimulus interval of 0,1 ms to 6 ms in steps from 0,1 ms with a biphasic pulse configuration (pulse duration: 160 µs). The bursts of the qTBS consist of 4 pulses. We applied an (i)-qTBS adapted to the individual I-waves over the same hotspot (M1-HAND). Subsequently, the motor evoked potentials (MEP) and the resting motor threshold (RMT) were recorded over the period of one hour (post1-4). Results. The statistical analysis (rmANOVA) of the i-qTBS in PA direction did not show changes of the MEP-amplitude comparing the pre- to the 4 post-readings (F(4, 44) = 1.314, p = .280). The i-qTBS in AP direction also did not show any changes in MEP-amplitudes (F(4, 40) = .462, p = .763) over the course of an hour. Discussion. An i-qTBS adapted to the individual I-wave latencies did not result in any changes of corticospinal excitability. Possible reasons for this might be the high number (>200) of pre-stimuli due to the SICF, or extinction phenomena of different I1-/I3-effects. Further studies on individualized stimulation are necessary in order to analyse the neurophysiological mechanisms of the effects. This will enable a targeted individual therapeutical application of qTBS in a clinical context.

Применение метода независимых каналов для определения электрической проводимости графеносодержащего шунгита.

The independent channel method which is intended for the calculation of specific electrical conductivity of graphene-contained shungite is proposed and realized on practice. It is noted that the most important of shungite application is the creation of screen hawing large area which are able to block electromagnetic radiation in wide frequency range. The most important factor which determines the blocking properties of shungite is the specific electrical conductivity of its carbon part which is determined by the spatial distribution of carbon atoms. As a main method of carbon structure investigation is mentioned the high-resolution raster electron microscopy which allows from the surface of specimen to receive the card of distribution of graphene slides and graphene packets. The spatial factor which determines the shungite conductivity is large anisotropy of single graphene slide which reaches three orders and more in the cases along and across the slide. The proposed method independent channels takes into consideration the arbitrary orientation of graphene packets relatively to direction of current flow. As a basis of method is employing the card of carbon spatial distribution which is received by raster electron microscopy method. The card is divided by parallel channels which transverse dimension is near or slightly exceeds the typical dimension of graphene packet. The channels are divided to square blocks which sides are equal to width of channel. The whole resistance of channel is formed by the successive connection of individual resistances of blocks. The resistance of whole card is determined by parallel connection of channels or averaging of resistance of all channels and following filling the whole area of card. The first step of analysis is the determination of advantage orientation of slides inside of every blocks. On the basis of determined orientation the block is filled by periodic structure which period is equal to the width of graphene slide and neighbouring interval. As a parameter which determines the orientation is used the angle between advantage orientation of graphene slides and axis of current flow between contacts. Owing to symmetry of task in comparison of current direction the limited meanings of corner is 0 and 90 degree. It is established two principal different cases of orientation: first – when determining angle is less than 45 degree and second when this angle is more than 45 degree. In the first case the current flows along the stripe with large conductivity. In the second case the current flows across these stripes so as through the stripes with low conductivity. It is found the smooth dependence of block resistivity from the angle of strip orientation. For the characteristic of area which is filled graphene slides it is proposed the coefficient of filling which is determined by binary discretization method. On the basis of analysis of slides orientation and filling coefficients are calculated the resistance of individual blocks. The resistances of all channels of investigated card are proposed. By using two methods – parallel connection and averaging over all channels it is calculated the specific electrical resistance and specific electrical conductivity of material as a whole. It is found that the received values of specific conductivity exceed the determined in experiment value in several (to 10) times. For the coordination of calculated value with experimental value it is made the variation of specific resistances of graphene slides and intervals between its. It id found that the calculation by method of parallel connection of channels ensures several better coordination than method of averaging. It is shown that the resistance is improved in the first turn by the increasing the resistance of interval between slides. In the quality of possible reason of decisive role of interval it is proposed the observed in experiment sharp non-homogeneity of relative arrangement of graphene slides. It is discussed the possible courses of further development of work. As a most important task it is proposed the more circumstantial determination of statistical character of received results.