Current Dissipation Research Articles

Innovative heat sink design for enhanced cooling efficiency in Dual Active Bridge (DAB) topology

Abstract After in-depth research and analysis, aiming at the heat generation mechanism and limitations of the current heat dissipation method, this paper proposes an innovative heat dissipation design scheme. By optimizing the structural design of the heat sink, the heat dissipation surface area is increased, thus achieving more efficient heat emission and maintaining the optimal operating temperature of the equipment. Experimental data show that this new heat dissipation design significantly improves the cooling efficiency, an increase of about 60%, and provides support for the performance improvement of high-power power products, which brings a reliable and efficient cooling solution for related industries.

Ultra‐Fast Weak Light Detectors Based on van der Waals Stacked 2D Semiconductor/h‐BN Heterostructures

AbstractFast and sensitive detectors for weak light are crucial in various fields like real‐time monitoring, medical diagnosis, and astronomy. However, photodetectors using 2D materials face challenges in achieving both a low detection limit for weak light and fast response. Here, a vertical vdW graphene/indium selenide (InSe)/hexagonal boron nitride (h‐BN) heterostructure on a gold electrode is provided, demonstrating an ultra‐low detection limit of 47.4 nW cm−2 and an ultra‐fast response speed of 327 ns. Vertical photodetectors feature nanoscale channel length, thus reducing scattering and recombination of carriers. The high potential barrier of multilayer h‐BN effectively blocks carrier transport, resulting in ultra‐low dark current and minimal power dissipation. Additionally, enhanced light absorption in InSe by the metal‐insulator‐semiconductor structure improves the sensitivity to weak light detection. More importantly, the built‐in field at the graphene/InSe interface can promote the separation of photo‐generated carriers to improve the collection efficiency. These factors jointly reduce the detection limit and response time simultaneously for weak light. This vertical vdW heterostructure comprising a 2D semiconductor/h‐BN offers a solution to make the majority of 2D semiconductors applicable in ultra‐fast weak light detectors.

A Data-constrained Analysis for Joule Heating as a Solar Active Region Atmosphere Heating Mechanism. I. Sunspot Umbral Light Bridge

Understanding the mechanisms underlying the heating of the solar atmosphere is a fundamental problem in solar physics. The lower atmosphere of the Sun (i.e., photosphere and chromosphere) is composed of weakly ionized plasma. This results in anisotropic dissipation of electric currents by Coulomb and Cowling resistivities. Joule heating due to dissipation of currents perpendicular to the magnetic field by Cowling resistivity has been demonstrated to be the main mechanism for the heating of a sunspot umbral light bridge located in NOAA AR 12002 on 2014 March 13. Here, we focus on the same target region and demonstrate the importance of further constraining our Joule heating model using observational data in addition to magnetic field, namely plasma temperature calculated from the inversion of spectroscopic data obtained from the Interferometric BI-dimensional Spectrometer instrument of the ground-based Dunn Solar Telescope. As a parameter in our analysis, temperature is demonstrated to have the highest sensitivity after magnetic field. We show that the heating of the light bridge is a highly dynamic event that necessitates utilization of 3D spatially resolved observational data for temperature rather than a 1D temperature stratification based on theoretical/semiempirical solar atmosphere models. Our improved data-constrained analysis using spatially resolved temperatures shows that the entire light bridge is heated by the proposed mechanism, and yields heating rate values that are consistent with our previous study.

Analysis of different test techniques of DC circuit breaker

Abstract Amidst the escalating demand for energy and the proliferation of renewable energy sources, direct current (DC) systems have garnered increasing interest. As pivotal for the safety and reliability of DC systems, testing DC circuit breakers is a critical step to evaluate their performance and dependability. This study focuses on the breaking test method for medium and high-voltage DC circuit breakers. It compares and evaluates the current waveform, recovery voltage, and energy dissipation across various test circuit methodologies during the breaking process of DC circuit breakers and assesses the suitability of test methods across different voltage levels.

Influence mechanisms of ultraviolet irradiation aging on DC surface discharge properties of silicone rubber in dry and humid air

In the modern DC electrical transmission system, high-energy photons interact with silicone rubber (SIR) chains during long-term ultraviolet (UV) irradiation, it degrades the surface properties and triggers surface discharge (flashover) along the SIR-air interface, threatening the secure operation of the advanced electrical equipment. To further comprehend how UV-aging influences the flashover performance, in this work, the chemical bonds, surface charge transport parameters, and flashover performance of UV-aged SIR samples are characterized, and the influence mechanisms of UV-aging on surface discharge in dry and humid air are comprehensively clarified through the investigation from “molecular-mesoscopic-macroscopic” scales. The results indicate both degradation and oxidization reactions occur during UV-aging. The degraded molecular chains dominate the discharge in dry air, while oxidization reactions determine the discharge in humid environment: The degradation reactions reduce the surface trap depth and increase surface conductivity, leading to large surface leakage current and surface charge dissipation rate, causing flashover voltage in dry air increases and decreases as UV-aging time increasing. The oxidization of the chains introduces –OH and –COOH groups into chains, enhancing permittivity and adsorbing H2O molecules, significantly increasing surface leakage current, causing surface discharge voltage in humid air to decrease as UV-aging time increases.

Design and Implementation of 6-T SRAM using FINFET

Abstract: SRAM is designed using conventional CMOS tech- nology to store data in memory. A lot of devices, including logic and memory, are having different issues as a result of the channel being lost of control. These include low leakage current, high power consumption, and short channel effects, which raise production costs and lead to significant changes in characteristics and decreased dependability. It is advised to employ FINFET based SRAM cells rather than traditional CMOS ones as a result of these problems. One of the primary elements that must be decreased in order to increase the stability of SRAM cellsis thought to be power dissipation and leakage currents. The amount of power dissipation and leakage currents can be de- creased using a variety of low power methods. These include the Self Controllable Voltage Level (SVL) technique, Power Gating, Stacking technique, Variable Threshold CMOS (VTCMOS), and Multi Threshold CMOS (MTCMOS). Here, we suggest designing a FINFET SRAM cell using the 28nm technological approach andcomparing its dynamic power consumption and stability to thatof the 8T FINFET SRAM cell. Every simulation is carried out using the Cadence Virtuoso Tool.

Wirelessly Powered and Bi-Directional Data Communication System With Adaptive Conversion Chain for Multisite Biomedical Implants Over Single Inductive Link.

A wirelessly powered and data communication system is presented which is implemented as a full system, designed for multisite implanted biomedical applications. The system is capable of receiving wireless power and data communication for each implant separately, using inductive links with different resonance frequencies. To achieve this, dual-band coils are presented in the system. In addition, the system supports bi-directional half-duplex data communication, utilizing amplitude and load shift keying (ASK and LSK) modulation schemes over a single inductive link. The system employs a digitally assisted active rectifier and an automatic resonance tuning system, to improve the power transfer efficiency (PTE) through various coupling coefficients, while minimizing the reverse current and power dissipation. The power control unit enables closed-loop monitoring to prevent high or low power delivery, and it can detect inefficient or excessive wireless power transmission or prevent temperature elevation by limiting the voltage to a safe level. A new structure of self-sampling separated- Vb ASK demodulator is proposed in the paper which is utilized within the data conversion chain, serving both the external and implanted units. The whole system is fabricated using a standard 180-nm 1.8/3.3 V CMOS process with a core area of 0.82 mm[Formula: see text]. The system is tested with coupled multisite inductive links and offers the maximum overall PTE of 31.2%, from the Tx coil to the implant load.

Design of high-K dielectric HSS-DMG Junctionless FinFET using hetero GOS for nanoscale application

This article presents a detailed investigation of the High-K dielectric horizontal stack spacer (HSS) dual material gate junction-less FinFET device for analog and RF application using the gate oxide stack (GOS) approach. At first, the impact of the horizontal stack spacer (HSS) with different high-K spacer materials are investigated by placing different dielectric material like HfO2, SiO2, Si3N4, and TiO2 on the horizontal spacer. The simulation results of the device indicate that the High-K dielectric HSS makes the device high stability toward the leakage current and static power dissipation at the sub-nano scale regime. The DC characteristics of the device are also investigated alongside the AC/RF characteristics. The proposed device predominantly improves performance in terms of parameters like subthreshold swing, Ion/Ioff, and DIBL. The proposed device shows a high ON current of 8.56 × 10−5 A μm−1, which is about 15% higher than the existing literature, and the device also makes a notable impact on the leakage current by restricting it to 9.635 × 10−12 A/μm. The simulation of the device is carried out with optimization of the doping to investigate and improve the device’s performance. The device shows an excellent improvement in performance which is highly suitable for future-ready device applications.

A 65 nm 75 MHz–260 MHz sixth-order Active-RC bandpass filter

-A sixth-order Chebyshev-I active-RC bandpass filter was fabricated in a 65 nm CMOS process. An operational amplifier (OPA) with an improved feedforward compensation structure is achieved, which significantly increases bandwidth and gain while reducing power consumption. The tuning module enables the filter to measure a center frequency of 75 MHz–260 MHz, and the bandwidth, Q-factor and gain can be configured according to different application requirements. The effective area of the filter chip is 0.64 mm2, and it can operate at a voltage of 2.5 V with a current dissipation of 34.3 mA.

Investigation of convective peristaltic flow of non-Newtonian fluids through a non-uniform tapered porous conduit with Ohmic heating and viscous dissipation

ABSTRACT The study of convective magnetohydrodynamic (MHD) biofluid transport through a non-uniform duct is of interest due to its applications to biomedical devices and equipment. Because of this, a comparative study of free convective peristaltic flow of non-Newtonian (Casson and Jeffrey) fluids in a tapered porous symmetric duct with Hall current and viscous dissipation effects is carried out. The proposed dimensional governing equations are converted into a system of non-dimensional partial differential equations by invoking adequate non-dimensional parameters. Furthermore, a long-wavelength approximation is used to reduce the complexity of the system. Then the reduced system of partial differential equations is solved analytically using the regular perturbation method. The fascinating features of the influential parameters on the flow characteristics are demonstrated and analyzed in depth through graphs and tables. The results demonstrate that the velocity and temperature in the Jeffrey fluid flow are larger compared to those in the Casson fluid flow. The thermal Grashof number and the Hall current parameter enhanced the pressure rise profile. This research has significant implications in biomedical devices (MRI, vitamins A and D injections, heart-lung machines, etc.) and pharmaceutical fluid preparation in biomedical sciences.

Flash viscous flow sintering of nanostructured amorphous ZrO2–Y2O3 composite ceramics starting from a partially amorphous precursor powder

Nanostructured amorphous composites are novel materials comprising nano-sized crystal phases embedded in an amorphous matrix, but often necessitating ultra-high-pressure molding for preparation. In this study, nanostructured amorphous ZrO2–Y2O3 composite ceramics were rapidly prepared for the first time using flash viscous flow sintering without the application of pressure. The relative density of the ZY ceramics increased with increasing current density, and ZY composite ceramics with relative density of 86%–97 % were prepared by FS in a short time of 60 s under 700 V/cm with 0.16–0.56 A/cm2. Furthermore, the sintering activities in FS were compared between partially amorphous powder and crystalline powder. The ceramics prepared by flash sintering of partially amorphous powder show a much higher relative density than that from crystalline powder, suggesting that partially amorphous powder achieves easier densification than crystalline powder in flash sintering under given current density and power dissipation. This phenomenon was attributable to the differing sintering mechanisms between the two materials, i.e., solid-state sintering for crystalline powder and viscous flow sintering for partially amorphous powder.

Sub-5 nm Ultrathin In2O3 Transistors for High-Performance and Low-Power Electronic Applications.

Ultrathin oxide semiconductors are promising candidates for back-end-of-line (BEOL) compatible transistors and monolithic three-dimensional integration. Experimentally, ultrathin indium oxide (In2O3) field-effect transistors (FETs) with thicknesses down to 0.4 nm exhibit an extremely high drain current (104 μA/μm) and transconductance (4000 μS/μm). Here, we employ ab initio quantum transport simulation to investigate the performance limit of sub-5 nm gate length (Lg) ultrathin In2O3 FETs. Based on the International Technology Roadmap for Semiconductors (ITRS) criteria for high-performance (HP) devices, the scaling limit of ultrathin In2O3 FETs can reach 2 nm in terms of on-state current, delay time, and power dissipation. The wide bandgap nature of ultrathin In2O3 (3.0 eV) renders it a suitable candidate for ITRS low-power (LP) electronics with Lg down to 3 nm. Notably, both the HP and LP ultrathin In2O3 FETs exhibit superior energy-delay products as compared to those of other common 2D semiconductors such as monolayer MoS2 and MoTe2. These findings unveil the potential of ultrathin In2O3 in HP and LP nanoelectronic device applications.

Chromospheric and coronal heating in an active region plage by dissipation of currents from braiding

The question of what heats the outer solar atmosphere remains one of the longstanding mysteries in astrophysics. Statistical studies of Sun-like stars reveal a correlation between global chromospheric and coronal emissions, constraining theoretical models of potential heating mechanisms. However, spatially resolved observations of the Sun have surprisingly failed to show a similar correlation on small spatial scales. Here we use unique coordinated observations of the chromosphere (from the IRIS satellite) and the low corona (from the Hi-C 2.1 sounding rocket), and machine-learning-based inversion techniques, to show a strong correlation on spatial scales of a few hundred kilometres between heating in the chromosphere and emission in the upper transition region in strong magnetic field regions (‘plage’). Our observations are compatible with an advanced three-dimensional magnetohydrodynamic simulation in which the dissipation of current sheets caused by magnetic field braiding is responsible for heating the plasma simultaneously to chromospheric and coronal temperatures. Our results provide deep insight into the nature of the heating mechanism in solar active regions.

Evaluation of left ventricular flow field changes after stress in patients with nonobstructive coronary artery disease using ultrasonic flow vector imaging.

Vector flow mapping and treadmill exercise stress echocardiography were used to evaluate and explore changes in the left ventricular (LV) flow field of patients with nonobstructive coronary artery disease. Overall, 34 patients with nonobstructive (<50%) left anterior descending coronary artery stenosis (case group) and 36 patients with no coronary artery stenosis (control group) were included. Apical four-, three-, and two-chamber echocardiographic images were collected at rest and during early recovery from treadmill exercise. LV flow field, vortex area, and circulation (cir) changes were recorded in different phases: isovolumetric systole (S1), rapid ejection (S2), slow ejection (S3), isovolumetric diastole (D1), rapid filling (D2), slow filling (D3), and atrial systole (D4). Intra- and inter-group differences were compared before and after exercise loading. The control and case groups demonstrated regular trends of eddy current formation and dissipation at rest and under stress. Compared with the control group, the case group had irregular streamline distributions. Abnormal vortices formed in the S1 and D3 apical segments and D1 left ventricular middle segment in the resting group. Compared with the control group, the resting group had decreased left ventricular S1 vortex areas and increased S3 vortex areas. The post-stress D1 and D3 vortex areas and D1 and D2 cir increased. Compared with at rest, after stress, the control group had decreased S1, S3, D2, and D3 vortex areas; increased S2, D1, D3, and D4 cir; and decreased D2 cir. After stress, the case group had decreased S3 and D2 vortex areas, increased D1 vortex areas, and increased S2, D1, D3, and D4 cir (P all < 0.001). Logistic regression and ROC curve analyses show that increased D1 vortex area after stress is an independent risk factor for stenosis in nonobstructive stenosis of coronary arteries (OR: 1.007, 95% CI: 1.005-1.010, P < 0.05). A D1 vortex area cutoff value of 82.26 had an AUC, sensitivity, and specificity of 0.67, 0.655, and 0.726, respectively. The resting left ventricular flow field changed in patients with nonobstructive left anterior descending coronary artery stenosis. Both groups had more disordered left ventricular blood flow after stress. The increased D1 vortex area after stress is an independent risk factor for mild coronary stenosis and may contribute to the assessment of nonobstructive coronary stenosis. VFM combined with treadmill stress is useful in evaluating left ventricular flow field changes in patients with nonobstructive coronary artery disease, which is valuable in the early evaluation of coronary heart disease.

Research Status of Heat Dissipation Technology for Electric Vehicle Drive Motors

Background:: The application of electric vehicles in daily life is becoming increasingly widespread. However, the heat dissipation issues of the electric motors directly impact electric vehicles' stability and safety. Thus, research on the heat dissipation of the electric motor is conducive to improving the reliability of the drive motor and ensuring the overall stability and safety of electric vehicles; there is a growing emphasis on the development trends of heat dissipation technologies for electric vehicle drive motors. Objective:: In order to meet the increasing requirements of electric vehicles for stability and safety and to solve the problems of low heat dissipation efficiency of electric vehicle drive motors, the size of heat dissipation devices, and the short life span caused by the high temperature of drive motors, the heat dissipation of drive motors is optimized and the heat dissipation structure is improved. Methods:: Based on the structural characteristics of heat dissipation of electric vehicle drive motors, various representative patents related to the current heat dissipation technology of electric vehicle drive motors are summarized. Results:: By summarizing a large number of patents on electric vehicle drive motor heat dissipation technology, it is concluded that the current research on electric vehicle drive motor heat dissipation mainly focuses on liquid heat dissipation or gas heat dissipation and that the main reason for the heat dissipation problem of electric vehicle drive motors is the low heat dissipation efficiency due to over-reliance on a single heat dissipation method, and the reliability is poor due to failure to reasonably control heat dissipation according to the need for heat dissipation. This paper proposes a new idea of heat dissipation for electric vehicle drive motors, which effectively combines liquid heat dissipation and gas heat dissipation. Moreover, the heat dissipation efficiency will be significantly higher than the existing heat dissipation scheme, and the proposed heat dissipation concept of "ondemand distribution" will effectively improve the utilization rate of the heat dissipation medium and reduce the heat dissipation cost and the reasonable heat dissipation structure will reduce the volume of the heat dissipation device. The reasonable heat dissipation structure will also reduce the volume of the heat dissipation device. In addition, the future development of heat dissipation technology for electric vehicle drive motors is also discussed. Conclusion:: The heat dissipation scheme proposed in this paper will effectively improve the heat dissipation problem of electric vehicle drive motors. Compared with the existing heat dissipation methods, the heat dissipation efficiency of the heat dissipation scheme proposed in this paper will be improved by more than 8.5%, and the service life of the drive motor will be extended by more than 5.1%, while the size of the electric vehicle drive motor will be reduced by 6%. More related patents will be invented in the future.

Thickness Effect of Copper Clips on Power Module Packaging Design

The superior switching performance of SiC MOSFETs compared to Si devices is limited by packaging-related issues. High electromagnetic parasitics which lead to high voltage overshoots, and higher power losses are the main challenges of high frequency operation. Hence, packaging design modification and optimisation are necessary to accommodate faster switching. Copper clips replacing the bonding wires show promising results in reducing stray inductances, while enhancing the current conduction and heat dissipation since the clip are in contact with a larger area of the semiconductor chip. Silver sintering instead of soldering further improves the electrothermal behaviour. This paper investigates numerically various thicknesses of the copper clips and their effect on double-sided silver sintering, half-bridge 1200V/400A SiC MOSFET power module. Moreover, the silver layer thickness is varied to reduce th maximum stresses on the chip - silver interface.

Highly Efficient Room-Temperature Nonvolatile Magnetic Switching by Current in Fe3GaTe2 Thin Flakes.

Effectively tuning magnetic state by using current is essential for novel spintronic devices. Magnetic van der Waals (vdW) materials have shown superior properties for the applications of magnetic information storage based on the efficient spin torque effect. However, for most of known vdW ferromagnets, the ferromagnetic transition temperatures lower than room temperature strongly impede their applications and the room-temperature vdW spintronic device with low energy consumption is still a long-sought goal. Here, the highly efficient room-temperature nonvolatile magnetic switching is realized by current in a single-material device based on vdW ferromagnet Fe3GaTe2. Moreover, the switching current density and power dissipation are about 300 and 60000 times smaller than conventional spin-orbit-torque devices of magnet/heavy-metal heterostructures. These findings make an important progress on the applications of magnetic vdW materials in the fields of spintronics and magnetic informationstorage.

Stratified materials for aircraft structure: thermal effect of lightning impact by numerical simulations

This paper studies the effect of lightning impact on aircraft fuselage made of innovative Carbon Fibers Reinforced Composites (CFRC) panels, as an alternative to traditional metal structures. Metal layers are able to dissipate the current generated by lightning impacting the structure, whereas the multilayer CFRC panels are less conductive and therefore have limited capacity for current dissipation. This study presents a time-varying thermal simulation coupled with an electromagnetic simulation, considering different lightning currents that represent both short strokes (i.e., impulses), and long strokes (i.e., square pulses). In order to compare different stoke shapes, the temperature increment resulting from the lightning impact will be assessed through Finite Element Analysis. This approach allows for an assessment of the impact of different strokes on CFRC panels. The model serves as a starting point for future analyses aimed at comparing different technological solutions, beginning with experimental laboratory tests.

Dissipationless Counterflow Currents above T_{c} in Bilayer Superconductors.

We report the existence of dissipationless currents in bilayer superconductors above the critical temperature T_{c}, assuming that the superconducting phase transition is dominated by phase fluctuations. Using a semiclassical U(1) lattice gauge theory, we show that thermal fluctuations cause a transition from the superconducting state at low temperature to a resistive state above T_{c}, accompanied by the proliferation of unbound vortices. Remarkably, while the proliferation of vortex excitations causes dissipation of homogeneous in-plane currents, we find that counterflow currents, flowing in the opposite direction within a bilayer, remain dissipationless. The presence of a dissipationless current channel above T_{c} is attributed to the inhibition of vortex motion by local superconducting coherence within a single bilayer, in the presence of counterflow currents. Our theory presents a possible scenario for the pseudogap phase in bilayer cuprates.

Non-bridge NTC thermistor anemometer with programmable sensitivity

This paper presents a programmable constant temperature anemometer (CTA) with a voltage control of the negative temperature coefficient (NTC) thermistor's working temperature. The CTA uses a non-bridge regulating circuit, outputting voltage, current and power dissipation signals. Its operation and sensitivity control are tested for NTC temperatures in a 45 to 85°C range, at wind speeds up to 14m/s. The power sensitivity at 25m/s is improved by NTC temperature increase, estimated to be 6.74mW/(m∙s−1) at 85°C. A qualitative analysis of circuit's stability is derived, providing the guidelines for bandwidth optimization. The NTC's resistance is regulated with error of 0.9% for working temperatures over 60°C. The demonstrated programmability of NTC temperature allows for implementation of known temperature compensation and measurement techniques utilizing a single sensor, while permitting continuous sensitivity control. This makes it suitable for measurements with varying ambient conditions.