Current Dissipation Research Articles

A 13.56-MHz -25-dBm-Sensitivity Inductive Power Receiver System-on-a-Chip With a Self-Adaptive Successive Approximation Resonance Compensation Front-End for Ultra-Low-Power Medical Implants.

Battery-less and ultra-low-power implantable medical devices (IMDs) with minimal invasiveness are the latest therapeutic paradigm. This work presents a 13.56-MHz inductive power receiver system-on-a-chip with an input sensitivity of -25.4dBm (2.88μW) and an efficiency of 46.4% while driving a light load of 30μW. In particular, a real-time resonance compensation scheme is proposed to mitigate resonance variations commonly seen in IMDs due to different dielectric environments, loading conditions, and fabrication mismatches, etc. The power-receiving front-end incorporates a 6-bit capacitor bank that is periodically adjusted according to a successive-approximation-resonance-tuning (SART) algorithm. The compensation range is as much as 24pF and it converges within 12 clock cycles and causes negligible power consumption overhead. The harvested voltage from 1.7 V to 3.3V is digitized on-chip and transmitted via an ultra-wideband impulse radio (IR-UWB) back-telemetry for closed-loop regulation. The IC is fabricated in 180-nm CMOS process with an overall current dissipation of 750 nA. At a separation distance of 2 cm, the end-to-end power transfer efficiency reaches 16.1% while driving the 30-μW load, which is immune to artificially induced resonance capacitor offsets. The proposed system can be applied to various battery-less IMDs with the potential improvement of the power transfer efficiency on orders of magnitude.

A New Look at the Electron Diffusion Region in Asymmetric Magnetic Reconnection

AbstractA new look at the structure of the electron diffusion region in collision less magnetic reconnection is presented. The research is based on a particle‐in‐cell simulation of asymmetric magnetic reconnection, which includes a temperature gradient across the current layer in addition to density and magnetic field gradient. We find that none of X‐point, flow stagnation point, and local current density peak coincide. Current and energy balance analyses around the flow stagnation point and current density peak show consistently that current dissipation is associated with the divergence of nongyrotropic electron pressure. Furthermore, the same pressure terms, when combined with shear‐type gradients of the electron flow velocity, also serve to maintain local thermal energy against convective losses. These effects are similar to those found also in symmetric magnetic reconnection. In addition, we find here significant effects related to the convection of current, which we can relate to a generalized diamagnetic drift by the nongyrotropic pressure divergence. Therefore, only part of the pressure force serves to dissipate the current density. However, the prior conclusion that the role of the reconnection electric field is to maintain the current density, which was obtained for a symmetric system, applies here as well. Finally, we discuss related features of electron distribution function in the electron diffusion region (EDR). Specifically, we analyze both new crescent substructures as well as outer, higher energy crescents generated by accelerated magnetospheric particles.

Modeling and simulation of micro-rotation and spin gradient viscosity for ferromagnetic hybrid (Manganese Zinc Ferrite, Nickle Zinc Ferrite) nanofluids

A common technique of enhancing thermal conducting is through the insertion of small magnetic particles or other nanoparticles with high thermal conductivity. In this research letter, manganese Zinc ferrite (MnZnFe2O4) and Nickle Zinc ferrite (NiZnFe2O4) were examined to assess the maximum possibility of enhancing thermal conductivity for current heat dissipation fluid problem. Therefore, a mathematical modeling is developed for steady, incompressible, 2D ferromagnetic hybrid (Manganese Zinc Ferrite, Nickle Zinc Ferrite) nanomaterial of micropolar fluid (non-Newtonian) towards moving surface of sheet. Darcy–Forchheimer porous medium effect is studied through momentum equation and thermal stratification effect is employed in heat equation. Micro-rotation and spin gradient effects are accounted. The model of heat diffusion initiated by Fourier law of heat conduction is implemented for energy transport assessment. The governing partial differential equations are altered through implementation of appropriate similarity variables into ordinary ones. Built-in-Shooting technique leads to the solutions of dimensionless flow equations. Behaviors of physical phenomenon are sketched by taking various positive estimations of concerning material constraints. The comparative solutions subject to manganese Zinc ferrite (MnZnFe2O4) and Nickle Zinc ferrite (NiZnFe2O4) hybrid nanofluids are presented and studied. From obtained results, we observed that velocity is more for MnZnFe2O4-NiZnFe2O4-C8H18 as compared to MnZnFe2O4-NiZnFe2O4-C10H22-C8H18 hybrid nanomaterials.

Structure and thermal properties of periodic split-flow microchannels

Microchannel heat sinks have important applications in integrated circuits, but the current traditional long straight microchannel heat dissipation process causes uneven temperature and low heat dissipation efficiency. In this paper, a periodic split-flow microstructure is designed and integrated with traditional microchannels to form a periodic split-flow microchannel heat sink. Numerical simulation is used to study the influence of the number, the arrangement and structural parameters of microstructures in a single microchannel on its thermal performance. The simulation results show that the split-flow microstructure can increase the heat exchange area, break the original laminar boundary layer, promote the mixing of cold/hot coolant, and significantly improve the heat dissipation performance of the microchannel. Through comparative experiments, 9 groups are finally determined as the optimal number of microstructures in a single microchannel. At a heat flux of 100 W/cm<sup>2</sup>, when the coolant flow rate at the inlet is 1.18 m/s, after 9 groups of microstructures are added into a single microchannel, the maximum temperature drops by about 24 K and the thermal resistance decreases by about 44%. The Nusselt number is increased by about 124%, and the performance evaluation criterion (PEC) reaches 1.465. On this basis, the microstructure adopts a staggered gradual periodic arrangement to avoid the long-distance non-microstructure section between the two groups of microstructures. The turbulence element that gradually widens along the flow direction makes the coolant fully utilized. This results in a reduction in the high/low temperature zone and alleviates the temperature gradient that exists along the flow direction of the heat dissipation surface, and the pressure drop loss is also reduced to a certain extent compared with the pressure drop in the uniform arrangement, and the comprehensive thermal performance is further improved. It shows broad application prospects in the field of high-power integrated circuits and electronic cooling.

Sustainable Lightweight Biochar-Based Composites with Electromagnetic Shielding Properties.

Global warming has prompted a search for new materials that capture and sink carbon dioxide (CO2). Biochar is a derivative of biomass pyrolysis and a carbon sink mainly used to improve crop production. This work explores the underlying mechanism behind biochar’s electric conductivity using a wide range of feedstocks and its combination with a binder (gypsum). This gypsum–biochar composite exhibits decreased density and flexural moduli with increasing biochar content, particularly after 20% w/w. Gypsum–biochar drywall-like composite prototypes display increasing shielding efficiency mostly in the microwave range as a function of biochar content, differing from other conventional metal (copper) and synthetic carbon-based materials. This narrow range of electromagnetic interference (EMI) shielding is attributed to natural alignment (isotropy) of the carbon ultrastructure (e.g., lignin) induced by heat and intrinsic interconnectivity in addition to traditional phenomena such as dissipation of surface currents and polarization in the electric field. These biomass-derived products could be used as sustainable lightweight materials in a future bio-based economy.

Effectiveness of Hall current and ion slip on hydromagnetic biologically inspired flow of Cu − Fe 3 O 4/H 2 O hybrid nanomaterial

Heat transfer augmentation is a significant concern in numerous engineering and industrial cooling/heating appliances nowadays. The usage of hybrid nanoliquids has been drawing attention of scientists in order to reduce the limitations of nanofluids and merge the chemical and physical characteristics of nanoparticles in an effective manner. Keeping such effectiveness in mind, present article aims to investigate the peristaltic flow of hybrid nanofluid with heat transfer and irreversibility analysis. Hybrid nanofluid is formed by mixing copper (Cu) and iron oxide (Fe 3 O 4) nanoparticles in water (H 2 O). The Cu − Fe 3 O 4 hybrid nanofluid with nanoparticles volume concentration 2% is used in this study. Impacts of Hall current, ion-slip, mixed convection and viscous dissipation are taken into consideration. Mathematical modeling for entropy generation is formulated via second law of thermodynamics. Governing equations of given problem are first converted into ordinary differential equations by employing lubrication approach. Obtained dimensionless equations are then tackled analytically with the aid of regular perturbation technique. Results reveal that temperature of hybrid nanofluid decreases by improving concentration of nanoparticles. Heat transfer rate at wall increases by improving Hartman number. Entropy generation reduces by improving Hall and ion-slip parameters. Bejan number increases by increasing Hartman number. Velocity of hybrid nanofluid increases by enhancing Grashof number. Pressure gradient of hybrid nanofluid increases by increasing Hall parameter. Pressure rise per wavelength decreases by enhancing ion-slip parameter. A comparison of temperature for base fluid, nanofluid and hybrid nanofluid is also furnished in tabular form. Additionally, comparison of numerical and analytical outcomes of velocity is also provided graphically. It is anticipated that the present study provides a theoretical data for the selection and design of hybrid nanofluid based heat exchanger.

Ranking of commercial photodiodes in radiation detection using multiple-attribute decision making approach

Recent studies have shown that silicon PIN photodiodes can be used in the area of detecting ionizing radiation. Selection of proper photodiode as ionizing radiation detector is crucial. In this paper the SMART technique as a subset of multiple-attribute decision making (MADM) approaches is employed in order to rank detectors. Using this method leads to the optimized initial selection of detector. The process of ranking is based on pre-defined attributes such as active area, breakdown voltage, minimum wavelength in the spectral range, wavelength with maximum response in spectral range, dark current, junction capacitance, and power dissipation of photodiodes. Evaluation results of a set of photodiodes show that PS100-6 and S1223-01 are the best and second-best alternatives, respectively. Considering commercial contemplations, cost could also be added to the aforementioned attributes. In this case, BPV10 and BPW34 are found as the best and second-best alternatives.

A 5-GHz Adjustable Loop Bandwidth Frequency Synthesizer With an On-Chip Loop Filter Array

The design of an adjustable loop bandwidth (LBW) frequency synthesizer with an on-chip loop filter (LF) array is presented. The LF array based on the simple capacitor multiplier topology is proposed to support LBW switching between 500 kHz and 1 MHz while saving 82.9% chip size compared to the traditional LF array. The maximum capacitance of 108 pF is realized by using the capacitor multiplier with an on-chip capacitance of 6 pF. The proposed frequency synthesizer is implemented in Taiwan Semiconductor Manufacturing Company (TSMC) 0.18-μm CMOS process and supplied at 1.8 V with a current dissipation of 11.8 mA.

Single Pulse Unclamped-Inductive-Switching Induced Failure and Analysis for 650 V p-GaN HEMT

This letter firstly reveals the single pulse unclamped-inductive-switching (UIS) withstanding physics and failure mechanism for p-GaN high electron mobility transistor (HEMT) with Schottky type gate contact. Unlike silicon/silicon carbide (Si/SiC)-based devices, the p-GaN HEMT withstands the surge current from load inductor by storing the energy into the output capacitance of the device, rather than dissipating the energy by avalanche process. To describe the UIS process, physics-based models are proposed. Also, by the simulations and de-cap/de-layer experiments, the failure mechanism is presented as a different manner compared with Si/SiC-based devices. The high voltage during the UIS process introduces high electric field near the drain contact, which leads to the inverse-piezoelectric effect, then bringing the rise-up of the leakage current and high power dissipation. As a result, the region near drain contact is burned by thermal runaway. Moreover, it is demonstrated that higher bus voltage and larger load inductance will increase the UIS-induced failure risk, while the gate resistance, turn- off gate voltage and ambient temperature exhibit little influences upon the UIS withstanding capability of the device.

Spatially dependent modeling and simulation of runaway electron mitigation in DIII-D

New simulations with the Kinetic Orbit Runaway electron (RE) Code KORC show RE deconfinement losses to the wall during plasma scrape off are the primary current dissipation mechanism in DIII-D experiments with high-Z impurity injection, and not collisional slowing down. The majority of simulations also exhibit an increase in the RE beam energy due to acceleration by the induced toroidal electric field, even while the RE beam current is decreasing. In this study, KORC integrates RE orbits using the relativistic guiding center equations of motion, and incorporates time-sequenced, experimental reconstructions of the magnetic and electric fields and line integrated electron density to construct spatiotemporal models of electron and partially-ionized impurity transport in the companion plasma. Comparisons of experimental current evolution and KORC results demonstrate the importance of including Coulomb collisions with partially-ionized impurity physics, initial RE energy, pitch angle, and spatial distributions, and spatiotemporal electron and partially-ionized impurity transport. This research provides an initial quantification of the efficacy of RE mitigation via injected impurities, and identification of the critical role played by loss of confinement due to plasma scrape off on the inner wall as compared to the relatively slow collisional damping.

Enhancing Security on IoT Devices via Machine Learning on Conditional Power Dissipation

The rapid development of connected devices and the sensitive data, which they produce, is a major challenge for manufacturers seeking to fully protect their devices from attack. Consumers expect their IoT devices and data to be adequately protected against a wide range of vulnerabilities and exploits. Successful attacks target IoT devices, cause security problems, and pose new challenges. Successful attacks from botnets residing on mastered IoT devices increase significantly in number and the severity of the damage they cause is similar to that of a war. The characteristics of attacks vary widely from attack to attack and from time to time. The warnings about the severity of the attacks indicate that there is a need for solutions to address the attacks from birth. In addition, there is a need to quarantine infected IoT devices, preventing the spread of the virus and thus the formation of the botnet. This work introduces the exploitation of side-channel attack techniques to protect the low-cost smart devices intuitively, and integrates a machine learning-based algorithm for Intrusion Detection, exploiting current supply characteristic dissipation. The results of this work showed successful detection of abnormal behavior of smart IoT devices.

Design Methodology for Distributed Large-Scale ERSFQ Bias Networks

Rapid single-flux quantum (RSFQ) circuits have recently attracted considerable attention as a promising cryogenic beyond CMOS technology for exascale computing. Energy-efficient RSFQ (ERSFQ) is an energy-efficient, inductive bias scheme for RSFQ circuits, where the power dissipation is drastically lowered by eliminating the bias resistors, while the cell library remains unchanged. An ERSFQ bias scheme requires the introduction of multiple circuit elements—current limiting Josephson junctions, bias inductors, and feeding Josephson transmission lines (FJTLs). In this article, parameter guidelines and design techniques for ERSFQ circuits are presented. The proposed guidelines enable more robust circuits resistant to severe variations in supplied bias currents. Trends are considered, and advantageous tradeoffs are discussed for the different components within a bias network. The guidelines provide a means to decrease the size of an FJTL and, thereby, reduce the physical area, power dissipation, and overall bias currents, supporting further increases in circuit complexity. A distributed approach to ERSFQ FJTL is also presented to simplify placement and minimize the effects of the parasitic inductance of the bias lines. This methodology and related circuit techniques are applicable to automating the synthesis of bias networks to enable large-scale ERSFQ circuits.

A Modeling Study of an Atmospheric Bore Associated With a Nocturnal Convective System Over China

AbstractBores have been shown to play a role in the initiation and maintenance of mesoscale convective systems (MCSs), particularly during the night after the boundary layer stabilizes. To date, the generation, evolution, and structure of bores over China has received little attention. This study utilizes observations and simulations with the WRF‐ARW model to investigate the generation and evolution of an atmospheric bore observed over Yangtze‐Huai Plains of China. The bore was associated with a nocturnal MCS that first formed over elevated terrain. The bore was observed ahead of the MCS with a maximum lateral extension of ~100 km. The feature lasted for over 90 mins and propagated at a speed of ~13 m/s, slightly faster than the MCS. In the simulation, the bore evolved from the separating “head” of the convectively generated gravity current. The bore then continued to propagate ahead of the MCS, even after the dissipation of the feeder current, and took on the appearance of an undular bore. The bore lifted a layer of convectively unstable air above the nocturnal surface inversion, initiating new convection ahead of the MCS to help maintain the MCS. The Scorer parameter ahead of the bore revealed a low‐level wind profile with curvature of the vertical profile of horizontal wind, favoring the trapping of wave energy and the persistence of the bore. These results are generally consistent with the role of bores in the maintenance of nocturnal MCSs and emphasize the need for future studies into the relationship between bores and nocturnal MCSs over China.

Распределенный электрический ток и его связь с ультрафиолетовым излучением активной области

Используя магнитограммы компонент вектора магнитного поля на уровне фотосферы, получаемые инструментом Helioseismic and Magnetic Imager (HMI), установленным на борту космического аппарата Solar Dynamics Observatory (SDO), вычислены вертикальные электрические токи для активной области NOAA 12192 за период с 22 по 25 октября 2014 года с временным разрешением 12 минут. Выявлено наличие в исследуемой активной области (АО) крупномасштабной токовой структуры – распределенного электрического тока, имеющего абсолютные значения в диапазоне (40–90)·1012 А. Предполагается, что распределенный ток охватывает всю АО, и, выходя в верхние слои солнечной атмосферы в одной части области, замыкается через хромосферу и корону на оставшейся ее части. Для проверки этого предположения проанализирована связь временных изменений величины распределенного тока с уровнем корональной активности, а также с интенсивностью ультрафиолетового излучения (УФ) АО в диапазонах длин волн 1600 Å, 304 Å, 193 Å и 94 Å. Показано, что: 1) Временные интервалы максимумов величины распределенного тока совпадают по времени с повышенной вспышечной активностью АО. Отсутствие резких изменений величины распределенного тока во время вспышек может быть объяснено высокой индуктивностью токонесущих петель. 2) Грубая оценка магнитной энергии, выносимой распределенным током в корону, дает для АО NOAA 12192 значения 1033–1034 эрг. Только небольшой объем этой энергии реализуется во время вспышечных процессов в АО, большая ее часть тратится на иные диссипативные процессы в короне. 3) Сравнение временных вариаций интенсивности излучения в канале 193 Å с динамикой распределенного тока в АО показывает хорошую взаимосвязь этих величин (коэффициент корреляции k = 0.63). В то же время отсутствует корреляции между величиной распределенного тока и интенсивностью УФ-излучения в диапазонах 1600 Å, 304 Å и 94 Å. 4) Полученные нами результаты, возможно, могут объясняться концепцией LRC-контура токонесущей корональной петли, предложенной в 1967 году Альфвеном и Карлквистом и развитой в работах В.В. Зайцева, А.В. Степанова и др. Согласно данной модели, крупномасштабные электрические токи должны существовать в верхних слоях солнечной атмосферы и принимать участие в нагреве коронального вещества.

Improving Performance of Nonvolatile Perovskite‐Based Photomemory by Size Restrain of Perovskites Nanocrystals in the Hybrid Floating Gate

AbstractPerovskite‐based photomemory adopting a floating‐gate architecture recently attracts research attention for developing efficient photo‐recording devices due to its simplified structure and non‐contact light‐programming feature. Herein, the memory characteristics of such type device is improved by the precise control of the size of perovskite nanocrystals (NCs) in the hybrid floating gate. Compared to the previous case of using polystyrene (PS) as the host polymer matrix, a N‐containing polymer, poly(2‐vinyl pyridine) (P2VP), is revealed to better regulate the size of embedded perovskite NCs into the nanometer level (7–9 nm) owing to the intense coordination between the N atom in P2VP and the Pb2+ ions of perovskite through Lewis acid‐base interaction. As benefitting from the reduced current dissipation and interfacial charge recombination at the gate/channel interface, the P2VP‐derived photomemory not only delivers a much higher On/Off current ratio (105) than the value (103) of the reference PS‐based device but also requires a much shorter illumination time (5 s) and low drain voltage (‐1 V) to achieve decent photo‐recording function. Besides, it possesses good long‐term retention for 104 s, excellent stress endurance over 100 cycles, and respectable ambient stability over 6 months due to the well isolation of perovskite NCs in the P2VP matrix.

Liquid Seepage in Coal Granular-Type Porous Medium.

To investigate liquid seepage process in a coal granular-type porous medium, a new sampling device was designed to obtain coal samples with required porosity. Meanwhile, an approach combining ultra-deep-field microscopy with advanced digital image processing technologies was proposed to rebuild granular-type porous medium models. The liquid seepage process was simulated with CFD, and the effects of head pressure, liquid viscosity, and pore size were studied. The results show that only liquids with head pressures above a critical value can penetrate into coal stacks and the hydraulic conductivity and permeability are positively correlated to the driving head pressure. Liquid viscosity enhances flow deformation, causing more eddy current energy dissipation; the turbulent eddy dissipation caused by acetone, methanol, and ethanol was 700, 1200, and 4700 m2/s3, respectively. Larger pores can strengthen the additional pressure at the front end of the flow, reducing the flow resistance and thus increasing the fluid kinetic energy and seepage velocity.

Spin-current dissipation in a thin-film bilayer ferromagnet/antiferromagnet

Ferromagnetic resonance in multilayer metal nanostructures containing an antiferromagnetic layer of variable thickness is studied. The contribution to the linewidth of the ferromagnetic resonance that is caused by spin-pumping current dissipation in an exchange-coupled antiferromagnetic/ferromagnetic bilayer is determined. The dissipative processes that occur in the bulk of the antiferromagnet and at the interface between the antiferromagnet (Fe50Mn50) and the ferromagnet (permalloy, Ni81Fe19) are distinguished. The details of how the dissipation transforms when the antiferromagnet Neel vector deviates from the direction of the exchange-pinning field are determined. The proposed method is effective for studying spin scattering in individual layers and at interlayer interfaces in complex magnetic systems.

Kinetic modelling of runaway electron generation in argon-induced disruptions in ASDEX Upgrade

Massive material injection has been proposed as a way to mitigate the formation of a beam of relativistic runaway electrons that may result from a disruption in tokamak plasmas. In this paper we analyse runaway generation observed in eleven ASDEX Upgrade discharges where disruption was triggered using massive gas injection. We present numerical simulations in scenarios characteristic of on-axis plasma conditions, constrained by experimental observations, using a description of the runaway dynamics with a self-consistent electric field and temperature evolution in two-dimensional momentum space and zero-dimensional real space. We describe the evolution of the electron distribution function during the disruption, and show that the runaway seed generation is dominated by hot-tail in all of the simulated discharges. We reproduce the observed dependence of the current dissipation rate on the amount of injected argon during the runaway plateau phase. Our simulations also indicate that above a threshold amount of injected argon, the current density after the current quench depends strongly on the argon densities. This trend is not observed in the experiments, which suggests that effects not captured by zero-dimensional kinetic modelling – such as runaway seed transport – are also important.

Sub-1-V BGR and POR Hybrid Circuit With 2.25-μA Current Dissipation and Low Complexity

Based on three groups of different offset voltages, a bandgap reference (BGR) and power-ON reset (POR) hybrid circuit is implemented in 65-nm CMOS. The BGR using amplifier offset voltage and current matching, and the POR using offset voltage comparison and loop settling feature, respectively, are proposed. This circuit, with low-quiescent current, not only generates a stable reference voltage independent of voltage and temperature variations, but also provides a high-robust supply-ramp-rate-tolerant power-ON/brown-out reset signal with a hysteretic window of 18–24 mV. Experimental results show that the circuit with line regulations (LNRs) of 2.63%–4.28%/V and temperature coefficients (TCs) of 22–32 ppm/°C across multiple chips has a power dissipation around $2.25~\mu \text{W}$ from a 1-V supply voltage. The circuit achieves a low noise density of 18.5 nV/ $\surd $ Hz at 100-Hz offset frequency and a good figure of merit (FoM) performance. With an active core area of 0.014 mm2, the circuit has fixed reset trip voltages under the supply ramp time of 0.4–100 ms.

Generation and dissipation of runaway electrons in ASDEX Upgrade experiments

The paper describes under which plasma and machine conditions runaway electrons (REs) are generated during ASDEX Upgrade plasma disruptions. The REs are created by argon injection to investigate methods of current and energy dissipation. The RE beams are stable and last up to a few hundred milliseconds. The experimental findings are described and made available for the validation of theoretical models. In the following, a simple 0D fluid model is used to simulate the observed RE current magnitude and time behavior. In spite of its simplicity, the model is consistent with the measured RE current. The injection of heavy gases into the RE beam is then discussed in some detail: the injected gas penetrates into the low density background plasma and through the beam without ionizing significantly. Therefore its effect on the REs can be tested directly and it is found to be consistent with the known Coulomb collisional theory.