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Na-ion batteries are growing interest due to their sustainability and low cost. A wide implementation in stationary applications, but also for short range transportation, is envisaged. This is further supported by the recent progress on Na-ion cells with increased energy density. To this regards, the development of procedures for real-time assessment of batteries state of health is of crucial relevance. The present paper provides an innovative procedure to assess sodium-ion battery capacity fading based on the application of discrete wavelet transform to voltage signals, acquired once a certain load pattern is applied at the battery terminals. The procedure development is provided through Na-ion cell aging test. During all the test battery capacity measurements are carried out. Root mean square error (RMSE) between assessed and measured values equals 1.18%. Moreover, during the aging test significant differences between performance evolution of Na-ion and NCR Li-ion cells are highlighted and discussed.

Equivalent circuit parameters of an induction motor are highly susceptible to various undesired factors. These phenomena primarily include effects of higher order time and space harmonics, temperature, magnetic saturation, and skin-effect. Traditional approaches model these equivalent circuit parameters via temperature, iron saturation, and slotting effects. However, the impacts of harmonic fields generated by the spatial magnetomotive force components as well as that of skin effect in motor inductances are not considered. The proposed work therefore presents an improved inductance estimation considering the impact of total harmonic distortion in the magnetomotive force with a power function-based formulation. Since the induction motor performance is sensitive to its rotor circuit parameters, another realistic variation taken up in this work includes the impact of iron saturation, and skin effect altogether on rotor leakage inductance and rotor bar resistance. Additionally, the effects of non-linearity, such as temperature variations, are incorporated into the magnetizing inductance, while the permeance of rotor tooth-bridge segments is considered in the rotor leakage inductance and bar resistance. The effectiveness of the proposed model is demonstrated with simulation and experimental results of a 13 kW three-phase induction motor prototype for a wide range of operations. This method significantly improves the modelling of inductances, enhancing the accuracy of the electromagnetic torque predictions over a wide range of operating speeds. Achieving net-zero carbon emissions is crucial for transportation electrification, which necessitates the use of high-speed traction motors in electric vehicles that require a reliable design. Therefore, an improved method is proposed that effectively captures the non-linear effects in predicting the parameters and performance including the output torque of the machine.

MEMS resonators with interdigital transducer (IDT) based on aluminum nitride (AlN) thin-film (a few micrometers thickness) materials gradually arouse researchers’ interest due to their ability to excite multiple modes of acoustic waves. However, the low electromechanical coupling coefficient is still one of the main reasons that limit the AlN-based resonators. In this article, we demonstrate a design journey for 10% scandium-doped AlN-based dual-mode acoustic wave resonators. Also, we investigated the influence of stack architectures with and without introduced AlN interlays, as well as the influence of stacked film thicknesses, on the performance of resonators. Simulation results show that changes in the SiO2 film thickness have different effects on the TCF of the two acoustic wave modes, providing a way for sensors to decouple two parameters that jointly affect the frequency drift. Moreover, measured results show that the introduced AlN interlayer (AlN-IL) induces a better crystalline orientation of the scandium-doped AlN (AlScN) thin film and a higher coupling coefficient of the leaky longitudinal (LL) mode (${K}^{{2}}$ : from 4.19% to 4.96%), which make the resonators have great potential in surface acoustic wave (SAW)-based applications such as sensors and high-frequency applications. [ABSTRACT FROM AUTHOR]

This work advances the research on continuous mode-reversal frequency modulated accelerometers by characterizing in depth some of their nonidealities, proposing methods for their compensation, and exploiting a renovated sensor design that enables closed-loop compensation of shock and vibrations. The scale factor nonlinearity is first investigated and compensated through a cubic calibration term, yielding a 50% larger range for a 2.5-fold larger scale factor than in former implementations. Additionally, temperature effects on the zero-g offset are compensated by exploiting the value of the low-pass filtered resonance frequency, which yields a valuable information of the silicon sensor temperature. This enables reducing the zero-g-offset temperature dependence by a factor 5 over previous works on similar structures. Finally, a closed-loop compensation of the quality factor, implemented through additional driving electrodes in the structure, guarantees a 25-fold reduction on effects of shocks and vibrations exciting the acceleration-sensitive mode. [2022-0117] [ABSTRACT FROM AUTHOR]

The temperature effect has been discussed in the past on pH sensors. In this study, the temperature effect is analyzed for the ascorbic acid (AA) biosensor based on enzymatic ascorbate oxidase (AO). To reduce this effect, a novel temperature compensation circuit was implemented by Taiwan Semiconductor Manufacturing Co., Ltd. (TSMC) 180 nm complementary metal-oxide-semiconductor (CMOS) process. By applying the proposed circuit, the temperature coefficients (TCs) with five concentrations of AA were suppressed below $201~\mathbf {\mu }\text{V}/\mathbf {^{\circ} }\text{C}$ . The TC of the normal level of AA concentration (0.0312 mM) in the human body was $188~\mathbf {\mu }\text{V}/\mathbf {^{\circ} }\text{C}$ , at the temperature range from 25°C to 55°C. The polyethylene terephthalate (PET) substrate was utilized. To confirm the stability of the fabricated AO/RuO2/PET AA biosensor, interference and hysteresis experiments were carried out. At present, the experiments were still in the stage of in vitro measurement. The results showed that the AO/RuO2/PET AA biosensor had good selectivity that effective against other interference that may exist in blood at either 25 °C or 37.5°C. Moreover, at the temperature of 37.5°C, the hysteresis voltage of the biosensor after applying the compensation circuit was reduced from 18.27 mV to 1.39 mV.

Electric vehicles (EVs) are booming all over the world for a low carbon emission and greener environment. The fast charging is an urgent demand for consumers. However, the dramatic temperature rising during high-power charging has a high risk of trigging thermal runaway and other safety issues. This article proposes an external liquid cooling method for lithium-ion battery module with cooling plates and circulating cool equipment. A comprehensive experiment study is carried out on a battery module with up to 4C fast charging, the results show that the three-side cooling plates layout with low coolant temperature provides better temperature control effect, while the coolant velocity and type have very weak impact. Then the simulation model with high precision is built for ultra-fast charging, and a safe charging range under 5C charging is proposed. The safe charging range under 5C can be increased by 50.1%. The environment close to the room temperature demonstrates the best effects of external cooling. For actual applications in the EVs, the circulating cooling equipment outside EVs can be integrated with high-power charging infrastructure and provide a 117 km improvement in mileage under 5C safe charging which indicates a tremendous application prospect. [ABSTRACT FROM AUTHOR]

Recent breakthroughs in Neural Networks (NNs) have made DNN accelerators ubiquitous and led to an ever-increasing quest on adopting them from Cloud to edge computing. However, state-of-the-art DNN accelerators pack immense computational power in a relatively confined area, inducing significant on-chip power densities that lead to intolerable thermal bottlenecks. Existing state of the art focuses on using approximate multipliers only to trade-off efficiency with inference accuracy. In this work, we present a thermal-aware approximate DNN accelerator design in which we additionally trade-off approximation with temperature effects towards designing DNN accelerators that satisfy tight temperature constraints. Using commercial multi-physics tool flows for heat simulations, we demonstrate how our thermal-aware approximate design reduces the temperature from 139 $^{\circ }$ ∘ C, in an accurate circuit, down to 79 $^{\circ }$ ∘ C. This enables DNN accelerators to fulfill tight thermal constraints, while still maximizing the performance and reducing the energy by around 75% with a negligible accuracy loss of merely 0.44% on average for a wide range of NN models. Furthermore, using physics-based transistor aging models, we demonstrate how reductions in voltage and temperature obtained by our approximate design considerably improve the circuit’s reliability. Our approximate design exhibits around 40% less aging-induced degradation compared to the baseline design. [ABSTRACT FROM AUTHOR]

The corrosion of transformers by multiple sulfides seriously affects the safe operation of transformers. However, there is a lack of quantitative characterization of the extent to which temperature and oxygen as well as changes in sulfide species affect the aging of oil–paper insulation. In this study, the aging characteristics of oil–paper insulation systems were analyzed in terms of the moisture in the oil, moisture in the paper, acid value, and furfural in the presence of multiple sulfides, where the temperature and the oxygen concentration are used as independent variables. A strong positive correlation between the acid value and the furfural obtained by means of Spearman’s correlation analysis. The acid value and furfural content in the oil were then analyzed and compared according to a nonparametric test, and it was found that both the oxygen changes and the temperature changes had a relatively obvious effect on the acid value in the oil. The effect of the temperature change on the furfural was greater than the effect of the oxygen change on the furfural. Finally, a multiple linear regression analysis was performed for the change in the acid value of the oil with the change in the oxygen content and temperature to obtain the linear fitting formulas for the effects of the time, temperature, oxygen content percentage, and sulfide groups on the acid value. This study can be used to quantify the magnitude of the influences of the oxygen, temperature sulfide groups, and other factors on the aging characteristic parameters of the oil–paper insulation system and to provide a certain reference for studying the quantitative characterization of the sulfur corrosion degree by using the change in the acid value in oil. [ABSTRACT FROM AUTHOR]

As the key cryogenic insulating material for high-temperature superconductivity equipment, epoxy resin works in the harsh environment of strong electric field and extremely cryogenic temperature, and its operational reliability faces severe challenges. In this article, aiming at bisphenol F epoxy resin for cryogenic insulation of super-conducting power equipment, researches on electrical trees in epoxy resin under lightning impulse voltage at room temperature and cryogenic temperature were carried out. The effects of temperature, impulse voltage amplitude, and polarity on the initiation characteristics, growth morphology, growth rate, and expansion coefficient of electrical trees are discussed. The results show that the electrical tree initiation under impulse voltage in a cryogenic environment also has a polarity effect. The voltage is higher than that under negative impulse voltage, the shape of electrical trees is a typical branch, the color is darker, the tree channel is wider, and the branches next to the channel are simpler. There are fewer branches, and many darker spherical or ellipsoidal cracks appear in the electrical branch channel. [ABSTRACT FROM AUTHOR]

Due to rapid temperature rise and insulation moisture, bubbles can generate in the oil-paper insulation of oil-immersed power transformers, which can reduce the dielectric strength of oil-paper insulation and even bring about the risk of insulation breakdown. In order to accurately evaluate the conditions of bubble formation, the physical process of bubble formation in oil-paper insulation is studied in this article. Considering the effects of water vaporization, gas dissolution in oil, and moisture migration on bubble formation, a bubble formation prediction model is constructed. Based on Henry’s law, the dissolution equilibrium of gas in oil is taken into consideration and the upper boundary of the initial temperature of bubble effect (ITBE) envelope is obtained in this model. Based on the moisture equilibrium in oil-paper insulation, the bubble formation process caused by the emergence and rapid evaporation of free water is analyzed, and then, the lower boundary of the ITBE envelope is obtained in this model. The model results show that the moisture content of the pressboard and the presence of free water have a great impact on ITBE. Specifically, the higher the moisture content, the lower the ITBE value. In addition, with the further increase of moisture content, the upper and lower boundaries of the ITBE envelope gradually tend to be the same. However, once free water is present on the surface of cellulose, ITBE decreases rapidly to below 120 °C. The model built in this article is of great significance to study the temperature limit of the power transformer. Hence the ITBE envelope can provide an important theoretical reference for reducing the risk of bubble formation during power transformer operation. [ABSTRACT FROM AUTHOR]

Transit-time flow meters need to compensate for cross-sensitivity to temperature. We show that Lamb wave-based setups are less affected by temperature. An optimality criterion is derived that allows to tune the meter into a zero local sensitivity to temperature. For this end, the flow-induced change in ultrasonic transit time is revisited first. While wetted piston transducer meters are directly sensitive to the change in propagation speed, the change in time of flight of Lamb wave-based systems is due to the beam displacement. Second, the effect of temperature is incorporated analytically. It is found that the temperature-dependent radiation angle of Lamb waves is able to compensate for changes in the speed of sound, leading to an (almost) unaffected overall time of flight. This effect is achievable with any fluid and in a wide temperature range. As an example, we discuss a water meter in the range from 0°C to 100°C. The model is validated against temperature and flow rate-dependent measurements obtained on a prototype. The measured data fits well to the developed model and confirms the reduced cross-sensitivity to temperature. Although an in-line meter is considered here, the results extend to clamp-on devices. [ABSTRACT FROM AUTHOR]

Taking into account the impact of self-heating and temperature rise effects, this work presents a physics-based analytical model for HEMTs, operating continuously from room temperature to high temperatures in linear and saturation regimes. Relying on the core École Polytechnique Fédérale de Lausanne (EPFL) HEMT model, the temperature dependence of various parameters including mobility, saturation velocity, critical electric fields, access region resistance, threshold voltage, and subthreshold slope was taken into account in the model. The accuracy of the developed model is validated by the TCAD simulation results and experimental data over a wide range of ambient temperatures from −20 °C to 500 °C. [ABSTRACT FROM AUTHOR]

The detection of solar-blind ultraviolet (SBUV) has received extensive attention from academia and the industry owing to the indispensable applications in many fields, based on which providing suitable photosensitive materials for SBUV photodetectors is necessary and important accordingly. In this study, ScOx films were fabricated by the solution method with the effect of annealing temperature on film quality as well as the performance of SBUV photodetectors analyzed. Combined with the effects from surface roughness and oxygen vacancy ratio of the films, it has been proved that the photodetector fabricated on a ScOx film annealed at 500 °C is an ideal one with the best performance exhibited. The fabrication method proposed in this research, that is, preparing ScOx SBUV photodetectors based on solution-processed films, both provides a new option of materials for SBUV detection and reduces the fabrication costs. [ABSTRACT FROM AUTHOR]

In this article, the surface charge characteristics of the direct current gas-insulated transmission lines (DC-GIL) insulator under thermal–electric coupled fields are investigated. A horizontally installed GIL with a basin-type insulator is employed. The 3-D charge distribution under different ambient temperatures, load currents, and gas pressures is obtained based on the finite-element method. It is found that the charge density increases with increasing ambient temperature since the bulk conduction is promoted due to the increasing insulator temperature. At lower ambient temperature, the surface charge distribution shows a more obvious difference in different radial directions along the insulator due to the increasing difference in electric conductivity in different directions. With increasing load current, the charge density increases, and the difference in charge density in different radial directions becomes more obvious. The charge density increases with increasing gas pressure although the temperature decreases, which is attributed to the domination of decreasing ion mobility over decreasing bulk conduction. It can be concluded that attention should be paid to these conditions when dealing with the insulation property of DC-GIL considering the effect of thermal gradient on the charge accumulation. Besides, simulation based on a 3-D model is necessary, especially for horizontal GILs. [ABSTRACT FROM AUTHOR]

SiC MOSFETs have received great attention due to their excellent electrothermal properties. Accurate junction temperature information of SiC MOSFETs ensures safe operation and helps effective thermal management. However, the existing thermal models have limits to correctly predict the thermal behaviors, whose parameter extraction processes are normally complicated. Most of the thermal models generally omit the temperature effects, which greatly impairs their usefulness and effectiveness. Here, a temperature-dependent physical resistor–capacitor (RC) network model is proposed, which can accurately characterize the thermal behavior of SiC MOSFETs particularly under high-temperature conditions. Meanwhile, the boundary conditions are fully investigated and modeled, which guarantees the adaptation of the proposed model for different real-field applications. The proposed method can remarkably simplify the process of parameter extraction since only the steady-state temperature distribution information is required with the assistance of finite-element method (FEM). Finally, the effectiveness and the robustness of the proposed model are validated by FEM simulation and experiments. [ABSTRACT FROM AUTHOR]

Topological spin textures are the next-generation spintronic building blocks for storing and processing information because of their controllable formation and annihilation. Memory, logic, and neuromorphic computing applications are reported using such devices having 2-D and 3-D spin textures, namely, vortex, skyrmions, localized bullet, and so on. A robust device-to-circuit-to-system level design is required for developing a neural network (NN) or a neuromorphic computing system (NCS) using these spin devices. Hence, in this work, we present a Verilog-A-based analytical model of a vortex spin-torque nano oscillator (V-STNO) for enabling circuit-level simulation. The model presented here is functional for both linear and nonlinear dynamics of the magnetic vortex core. The nonlinear dynamics show the formation and annihilation of the magnetic vortex depending on its critical currents. Furthermore, the developed model is analyzed for the nanopillar’s diameter and free layer thickness variations. Moreover, an investigation of the temperature effect on the device performance for a range of −40°C to 140 °C is carried out. [ABSTRACT FROM AUTHOR]

In this article, a pyroelectrically charged fluorinated ethylene propylene (FEP) piezoelectret force sensor is reported. The proposed pyroelectric charging technique provides reproducible and tunable charge generation. Pyroelectric charging is simple and compact when compared to other ferroelectret charging methods, such as corona discharge and dielectric barrier discharge and irradiation, which require high-voltage sources, sharp tips, and vacuum setups. In this pyroelectric charging study, temperature ramp rates of 1 °C/s (dT $=15^{\circ }\text{C}$), 2 °C/s (dT $=30^{\circ }\text{C}$), and 4 °C/s (dT $= 60\,\,^{\circ }\text{C}$) are applied to a lithium niobate pyroelectric crystal using a programmable temperature control system. The effects of the temperature ramp applied to the pyroelectric crystal and the number of temperature ramps on the piezoelectret charging are assessed. The pyroelectrically charged FEP piezoelectrets show ${d}_{{33}}$ piezoelectric coefficients up to 68.6 pC/N. The output of the FEP sensors is linear with the force and independent of frequency in the range of 45–505 Hz. The charge retention was assessed, showing no degradation of the piezoelectric activity up to 66 h. Finally, the FEP ferroelectret sensors were used in a pressure sensor array, allowing the recording of a human step (gait analysis experiment). [ABSTRACT FROM AUTHOR]

Soft magnetic composite (SMC) is composed of ferromagnetic particles surrounded by an electrical insulation layer. The unique structure of SMC makes it difficult to calculate the eddy current loss of SMC. In addition, the temperature rise in the working condition affects the magnetic properties of the material, which makes it necessary to consider the temperature effect in the process of core loss prediction. In this paper, a magnetic property test platform that considers the influence of temperature is established. The core losses of the SMC ring sample were measured at 20–100 °C, and the experimental results show that core loss decreases as the temperature increases. Then, based on the method of using the SMC model to calculate the core loss, the effect of temperature increase on hysteresis loss and eddy current loss was analyzed, and the existing model was improved to consider the effect of temperature on the core loss. Finally, the measured core losses at different temperatures were compared with the calculated ones, and it is shown that the improved model considering the influence of temperature agreed well with the experimental results, which improves the accuracy and convenience of core loss calculation for the electromagnetic device with SMC cores.

Reading data at a temperature which different from writing can cause a large number of failed bits in 3D NAND Flash memory. In this work, the threshold voltage (Vth) temperature effect of 3D NAND flash memory cell was investigated and a method was proposed to optimize its temperature coefficient (Tco). The results suggested that the Tco of low temperature programmed high temperature read is larger than high temperature programmed low temperature read and this difference is about 2-3mv/°C, which makes against the temperature compensation of reading voltage and lead to irreparable data errors even there is error correction codes. Furthermore, the critical factor of this difference was demonstrated that is the charge loss during low temperature programmed high temperature read and the Vth shift caused by charge loss is up to 30 percent. Based on this, we proposed to optimize the Tco consistency by shortening the interval time of erase to program in endurance cycling stage and confirmed that this method is effective by experiment. As the time interval becomes smaller, the difference of the Tco decreases as well, which have great reference signification for improving the reliability of 3D NAND flash memory.

To solve the problems of high cost of Cu nanoparticles (NPs) and high bonding temperature of Cu microparticles (MPs), a Cu2O NP-coated hierarchical structure (Cu-MP@Cu2O-NP) was proposed and fabricated for low-temperature Cu–Cu bonding. The Cu-MP@Cu-NP particles were obtained by Cu MPs through preoxidation and in situ reduction process, which formed a Cu particle with micro–nano core–shell hierarchical structure. The effect of preoxidation temperature on morphological features of Cu-MP@Cu2O-NP particles and mechanical properties of bonded joints were investigated. After reduction process, the generated Cu2O NPs on the surface of the hierarchical structure were reduced to Cu NPs completely. The surface NPs significantly enhanced the sinterability and structure density. After sintering at 300 °C, the shear strength of the bonded joints improved to 23.7 MPa, which is higher than that of Cu MPs without hierarchical structure. A sintering mechanism of Cu-MP@Cu-NP particles was proposed, revealing the surface NP layer is the key factor in this bonding process. [ABSTRACT FROM AUTHOR]

In this letter, we have proposed modifications to the existing BSIM-CMG compact model to enhance its ability to model the behavior of short channel bulk FinFETs (both n and p-type) from room temperature down to cryogenic temperatures (10K). The proposed model is highly accurate in capturing the subthreshold swing, threshold voltage, and effective mobility trends observed in FinFET cryogenic operation. For efficient optimization of the proposed model parameters, we have proposed an adequate modeling strategy. We have compared convergence time between the existing BSIM-CMG model and the proposed model by simulating a reasonably large circuit using pseudo-inverters. [ABSTRACT FROM AUTHOR]

Temperature can change the charge injection and migration characteristics in the liquid, affecting the insulation performance. First, the influence of temperature on the permittivity and Kerr constant of the liquid dielectric is studied. Also, the results prove that the permittivity and Kerr constant of propylene carbonate (PC) decrease with the increase of temperature. Moreover, to explore the influence of temperature on the insulation performance of propylene carbonate, we build a temperature-controllable breakdown test platform under voltage impulse, and the breakdown voltage of PC increases slightly with the increase in temperature. Based on the electrooptic effect, an optical platform is built to measure the electric field under the switching overvoltage. In addition, the space charge distribution is calculated, and the results indicated that the temperature in the range of 10 °C–40 °C is negatively correlated with the net space charge injection. Finally, the temperature effect on the rate of change and mobility of the space charges is explored. [ABSTRACT FROM AUTHOR]

Ge-doped optical fibers (OFs) are considered radiation-tolerant waveguides. Even if their transmission in the infrared (IR) domain is degraded under irradiation, for most of the applications, their radiation-induced attenuation (RIA) remains acceptable. Space harsh environment is characterized by low dose and dose-rate constraints meaning that germanosilicate fibers are often employed for data links. However, the temperature can largely vary in space and is known to impact the RIA levels and kinetics. We studied here systematically the combined temperature and radiation effects induced on the transmission, at the telecom wavelengths, of a Ge-doped fiber, between −80 °C and 80 °C up to a total ionizing dose (TID) of 10 kGy(SiO2)–1 Mrad. Our measurements highlight larger RIA levels at low temperatures than at room temperature (RT). At our highest TID, it increases by a factor of ~40 and ~20, respectively, at 1310 and 1550 nm, when the irradiation is performed at −80 °C instead of RT. A model is reported to study the activation energy of the radiation-induced point defects responsible for the IR-RIA. This simple model could help in predicting the fiber vulnerability for various mission profiles. [ABSTRACT FROM AUTHOR]

This article reviews the effects of applied bias and temperature on Si/SiO2 interface-trap buildup and annealing rates. Electrical and spectroscopic methods are described to estimate interface-trap densities at oxidized Si surfaces, in MOS capacitors and transistors, and in linear bipolar devices. Illustrative results provide insights into the kinetics and energetics of interface-trap annealing. Interface traps in MOS and linear bipolar devices anneal much more easily at 0 V bias than at positive or negative applied bias. Hydrogen transport and reactions play critical roles in interface-trap buildup and annealing processes. The complex interplay between H2 diffusion and H+ drift is illustrated via coupled experimental and theoretical studies. Interface-trap annealing imposes significant constraints on hardness-assurance techniques. Current MOS standard tests that incorporate accelerated aging at elevated temperature at worst case, static, positive bias enable successful assessment of MOS devices in low-dose-rate environments. However, it is not similarly possible to use elevated-temperature irradiation and/or annealing at worst case, 0 V bias to predict low-dose-rate response for linear bipolar devices and ICs. Temperature-switching during irradiation appears to be a promising approach to address this issue. [ABSTRACT FROM AUTHOR]

Resistive RAM (RRAM) or memristors are a class of electronic device whose resistance depends on voltage history. The changes in resistance can be divided into two categories, volatile and non-volatile. To date, the characteristics of non-volatile switching have been explored extensively with volatile switching behaviour still remaining more obscure. Here we investigate the temperature effects on TiOx based memristor volatility, and integrate these observations into a previously developed model for volatile switching. We show how device temperature affects the magnitude of the volatile resistive state in response to input stimulation, as well as the corresponding relaxation time constant. Importantly, these effects are polarity dependent. This work is part of an effort towards building a more comprehensive model of RRAM behaviour covering volatile and non-volatile phenomena as well as various environmental effects on them. [ABSTRACT FROM AUTHOR]

In this article, we propose an efficient methodology for the electrothermal characterization of power amplifier (PA) integrated circuits. The proposed electrothermal analysis method predicts the effect of temperature variations on the key performances of PAs, such as gain and linearity, under realistic dynamic operating conditions. A comprehensive technique for identifying an equivalent compact thermal model (CTM), using data from 3-D finite element method thermal simulation and nonlinear curve fitting algorithms, is described. Two efficient methods for electrothermal analysis applying the developed CTM are reported. The validity of the methods is evaluated using commercially available electrothermal computer-aided design (CAD) tools and through extensive pulsed RF signal measurements of a PA device under test. The measurement results confirm the validity of the proposed electrothermal analysis methods. The proposed methods show significantly faster simulation speed compared with available CAD tools for electrothermal analysis. Moreover, the results reveal the importance of electrothermal characterization in the prediction of the temperature-aware PA dynamic operation. [ABSTRACT FROM AUTHOR]

Temperature rising is an unavoidable effect on VLSI and has always been a critical issue in any system-on-chip – especially when targeting compute-intensive applications. This effect increases the delay in hardware accelerators, resulting in timing errors due to unsustainable clock frequency, whose impact must be carefully evaluated on design time to measure the performance degradation of the hardware accelerator. Further, a hardware operating at a higher temperature accelerates device aging, which incurs in more timing errors. This issue is usually addressed with the inclusion of timing guardbands that compensate for the deleterious effects of temperature, ensuring the hardware accelerator works within a reliable zone, i.e., without any timing errors caused by temperature effects at runtime. However, guardbands directly result in considerable performance and efficiency losses because the circuit will be clocked at a frequency lower than its full potential. Accelerators on edge devices often dismiss such guardbands to explore the full potential of the designed circuits, posing an enormous design challenge as this approach requires a careful evaluation of the impact of timing errors on the quality of the target applications. Many algorithms, such as in multimedia and machine learning applications, are capable of tolerating hardware errors. Yet, these algorithms have a dynamic behavior (i.e., closed-loop) where a timing error can be propagated, affecting subsequent steps. Measuring the degradation-induced errors in these applications is very challenging given that an accurate gate-level simulation to investigate degradation-induced timing errors needs to be coupled dynamically with a system-level simulator to unveil how induced errors in the underlying hardware ultimately impact the algorithm execution in the hardware accelerator. This is the first work to achieve this goal. State-of-the-art works have studied accelerators under timing-errors when removing (or narrowing) guardbands. However, their approach was suitable only for open-loop hardware accelerators which are entirely agnostic of complex interactions of the algorithms. Unlike prior work, this paper investigates temperature- and aging-induced timing-errors in the joint accelerator-algorithm interactions and their runtime impacts. Our framework investigates aging effects across the different layers starting from transistor physics all the way up to the algorithm layer. The hardware accelerator employed as a case study in this work is the sum of absolute differences (SAD), which is the most compute-intensive accelerator on commercial video encoder for mobile applications. Our results demonstrate the runtime behavior impacts of three advanced block-matching algorithms of the video encoder in a joint operation by a SAD accelerator under timing-errors induced by temperature and aging effects considering a 14nm FinFET technology. [ABSTRACT FROM AUTHOR]

In this study, we demonstrate that the length and distribution of the aggregates were dependent on the temperature of the aqueous solution of poly($N$ -isopropylacrylamide) (PNIPAM). Magnetic resonance relaxometry, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were used to observe the chaining of magnetic polymer nanoparticles (NPs) on a micrometer scale under a $0.3T$ magnetic field. As the temperature increased, the magnetic interparticle interactions increased, therefore increasing the chain formation. By utilizing the temperature-mediated lower critical solution temperature (LCST) of PNIPAM from hydrophilic to hydrophobic at 45 °C, multiple-thick-chain-like structures can be obtained. [ABSTRACT FROM AUTHOR]

The dynamic magnetic characteristic curves of TbDyFe alloy (TbxDy1−xFe1.9–2.0, $0.27 \leq x \leq 0.3$) under varying temperatures at different high-frequency excitation conditions were measured. The results show that when the excitation amplitude and frequency keep constants, the dynamic hysteresis loop, the permeability, and the magnetic energy loss all vary with the increase in temperature (from 10 °C to 80 °C). Their trends of temperature dependence are analyzed in detail. Based on the Bertotti loss separation method and experimental data, a magnetic energy loss calculation model for TbDyFe alloy under variable temperature conditions is proposed. The model considers the influence of high-frequency hysteresis characteristics and skin effect. It introduces temperature-related terms to modify the loss coefficients. The calculation results are compared with the experimental ones at different temperatures. It shows that this calculation method can accurately calculate the magnetic energy losses under variable temperature at higher frequencies (1–20 kHz). This research can provide an experimental and theoretical support for high-frequency engineering application of magnetostrictive materials. [ABSTRACT FROM AUTHOR]

Gap-type amorphous silicon (a-Si) thin-film transistor (TFT) can provide high photo current in simple device structure, which makes it suitable for large-area-sensing applications. The reason why the photo current is much higher when the device is operated in the on-region than that in the off-region is not well studied. In this article, we propose the mechanism to explain this special phenomenon for the gap-type a-Si TFT. The feature of potential well is supported by TCAD simulation. The mechanism is further verified from the perspective of temperature effect and time response. [ABSTRACT FROM AUTHOR]

The rheological behavior of magnetorheological fluids (MRFs) is greatly influenced by many key parameters such as concentration, composition, temperature, and magnetic field. As magnetic particles are dispersed in a non-magnetic liquid, MRFs exhibit an increase in viscosity with increasing magnetic fields due to the formation of chain-like structures. However, this viscosity change has often been studied as a function of any one or two of the key parameters. Herein, we studied the simultaneous effect of temperature, magnetic field, concentration of dispersed phase, and MRF composition on the viscosity of MRFs. Understanding the simultaneous effect of tunable parameters such as temperature and magnetic field allows for optimization of MRF performance and enhanced viscosity in commercial applications. Rheological experiments were performed on MRFs over a wide range of temperatures (15–65 °C) under magnetic fields between 0.1 and 1 T. The thermo-magnetorheological response was also studied with varying magnetic particle concentration (1 vol%–25 vol%) and MRF composition (both dispersed phase and carrier liquid). The results demonstrated a strong influence of magnetic particle composition and concentration on the MRF viscosity along with temperature while the carrier liquid composition had relatively negligible influence. [ABSTRACT FROM AUTHOR]

Advanced field programmable gate arrays (FPGAs) utilizing substrates with a thick organic core showed substrate core cracking after thermal cycling. These substrates are laminate structures with a core made from stacked layers of glass fiber and resin with routing layers made of copper and a dielectric build-up polymer. This type of cracking typically occurs on the glass fiber–resin interface, can penetrate several millimeters and across thru-vias to cause electrical failures, and was found on several test vehicles, four of which are detailed here. This work observed numerous examples to identify the characteristics of the cracking and notes the best observation practices. We hypothesize that this cracking is due to free edge effect at cold temperature. Since the free edge cannot have normal stress, a large out-of-plane stress exists at the edge and concentrates at the corner. Models were built to study the effects of various package parameters on the failure mode. The primary contributions to the free edge effect are the low-coefficient of thermal expansion (CTE) glass fiber, the high-CTE resin, and the high-CTE build-up layers. The trend toward lower CTE substrates has demanded lower CTE glass fiber material, which exacerbates this problem. Increasing complexity of routing demands additional layers, which also increases the out-of-plane stress at the corner. Other less significant factors that increase the stress include lower resin CTE, higher build-up CTE, and decreasing core thickness. Thru-via placement and dicing optimization had small impact and the substrate had negligible impact. [ABSTRACT FROM AUTHOR]

This article introduces a temperature-dependent demagnetization model and presents a generalized algorithm to deal with temperature-dependent demagnetization curves for permanent magnet materials. It supports the input of both intrinsic curve type and normal curve type. The algorithm is based on the intrinsic curve type. If the input curves are of normal type, they will be converted into intrinsic type and be extended to the whole second quadrant. The presented algorithm is validated by comparing the derived curves at specified temperatures with the original vendor-provided temperature-dependent demagnetization curves of various permanent magnet (PM) materials. The temperature effects on the performance of permanent magnet machines are illustrated in two application examples. [ABSTRACT FROM AUTHOR]

The most sensitive THz detection is obtained with superconducting Josephson Junction (JJ) detectors, cooled by liquid helium. These detectors require complex cooling systems. JJ detectors implemented in High Temperature Superconductors (HTSC) are considered a viable and more applicable alternative. The frequency of the detected radiation is directly proportional to the voltage of the Shapiro steps. To investigate temperature dependence of the frequency selectivity, i.e., the accuracy of the measured voltage, we implemented JJs detectors in YBa2Cu3O7 HTSC thin films, patterned on MgO bicrystal substrate. We improved the detector sensitivity and reduced losses by placing the JJ between the ends of two strips integrated with the antenna, reducing the high mismatch between the impedance of the JJ and that of the Au bow-tie planar antenna. The detector parameters were determined by extensive simulations. High correlation was obtained between the simulations and the experimental results. Error in the measured ${{\boldsymbol{V}}_{{\boldsymbol{DC}}}}$ , hence in the radiation frequency, was 3.5-7% at 60-70 K, 3-4 orders of magnitude larger than that measured at 40-50 K, less than 0.01%, showing the very strong influence of temperature on the frequency selectivity of high temperature JJs detectors. [ABSTRACT FROM AUTHOR]

In this article, an electromagnetic–thermal coupling algorithm based on the discontinuous Galerkin time-domain (DGTD) and spectral-element time-domain (SETD) methods is proposed, which can adopt two independent grids for thermal simulation and electrical simulation, respectively. It employs time-domain solvers for both the electrical and thermal fields. Compared with the conventional cosimulation scheme (e.g., time-domain solvers for the thermal field and frequency-domain solver for the electrical field), it can provide better simulation precision for problems characterized with small size or drastic field changes. By comparing the results of electromagnetic–thermal coupling simulation with the results of electromagnetic simulation, the effect of temperature change on electromagnetic field propagation is analyzed. [ABSTRACT FROM AUTHOR]

The paper investigates the role of the space charge accumulation phenomena in the inception of Partial Discharges (PD) in a defect within the bulk of the dielectrics of a High Voltage Direct Current (HVDC) cable. It is widespread accepted that the number of PD occurring in an HVDC cable during its lifetime is largely less than that under AC voltage stress. This is essentially due to higher values of the voltage between the conductor and the screen needed to trigger PD under a steady DC voltage than the same value under AC stress. Nevertheless, due to the dependency of the electrical conductivity of the insulation on the electric field and temperature, PD in HVDC cables is strongly influenced by the temperature distribution and, consequently, on the load current. Thus, the main goal of this research is to evaluate the main parameters of the PD occurring in an HVDC cable during a load transient. Numerical simulations by using Comsol Multlphysics® are validated by the results obtained with an ad hoc experimental setup. A model DC cable, subjected to transient phenomena due to a current step and with an air void defect in the insulation material, is simulated and setup. On the other hand, an experimental setup is used to carry out PD measurements on the same case study. The results of this research show the strong dependency of the PD parameters on the temperature distribution varying over time during a load transient. [ABSTRACT FROM AUTHOR]

PEEK (Polyetheretherketone) and N2 are used as the frame material and insulation gas in the packaging of high voltage power electronic devices, respectively. Considering the IGBT device in normal operation, the chip will produce a large amount of Joule heat, which will increase the temperature of the insulation material in sub-modules. However, there has been no investigations on the influence of temperature on the surface discharge characteristics and mechanisms under positive repetitive square voltage (PRSV). In this paper, surface discharge current pulses and optical photos of surface streamer propagation of PEEK in N2 at different temperatures are collected under PRSV. The effects of different temperatures on discharge current pulse, charge quantities of discharge and time delay of discharge are analyzed in detail. Besides, the surface trap parameters at different polarization temperatures are measured by TSDC. The effects of temperature on the effective ionization rate, surface trap depth and densities are revealed. A reasonable model is used to explain the role of surface traps in the streamer propagation along the surface of PEEK. Besides, the time delay theory is introduced to quantitatively analyze the effect of temperature on the time delay of forward discharge (FD) and backward discharge (BD). The influence mechanism of temperature on specific pulse parameters of discharge current, time delay of discharge and charge quantities of discharge are all analyzed on the basis of the trapping and detrapping of surface electrons and ions at different temperatures. [ABSTRACT FROM AUTHOR]

Pulsed electric fields (PEFs) had the potential to be a new pasteurization technology due to its advantages of energy-saving, high efficiency, and less influence on food quality based on the electroporation effect of PEF on microorganisms. At the same time, temperature played a significant role in the electroporation process. We established a two-membrane dielectric model that coupled temperature and PEF to study the influence of temperature on the dynamic process of electroporation. In this model, we considered both the effect of Joule heat on temperature generated by PEF and the effect of temperature on the conductivity of suspension, cytoplasm, nucleus, the characteristic voltage of electroporation, and molecules transport. The simulation results showed that under the higher ambient temperature, the transmembrane voltage of the cell membrane after electroporation could be stabilized at a higher value, the maximum value of membrane conductivity and pore density on the cell membrane was higher. The relationship between pore radius and temperature was simulated. What is more, temperature facilitated molecules transport, which intensified the destruction of cell homeostasis. [ABSTRACT FROM AUTHOR]

Temperature sensitive electrical parameter (TSEP) approaches are widely employed in the junction temperature ($T_{j}$) detection and prediction of power devices, especially the switching parameter. In this article, the voltage-rise time and its loss during the turn-off process are used as the TSEP index for the detection of junction temperature because of the coupling relationship with the maximum junction temperature. In addition, the effect of junction temperature on the current-fall time and its loss is compared. The theoretical analysis is verified by SABER simulation and H-bridge inverter circuit platform. It is established that the model based on voltage-rise time ($t_{\mathrm {rv}}$) and voltage-rise loss ($E_{\mathrm {rv}}$) is a viable model with good linearity, fixed sensitivity, and offers nondestructive insulated gate bipolar translator (IGBT) junction temperature extraction. [ABSTRACT FROM AUTHOR]

We present compact models that capture published cryogenic temperature effects on silicon carrier mobility and velocity saturation, as well as fully depleted silicon on insulator (FDSOI) and fin field effect transistor (FinFET) devices characteristics within the industry-standard Berkeley short-channel IGFET model (BSIM) framework for cryogenic IC applications such as quantum computing. For the core model charge density/surface potential calculation, we introduce an effective temperature formulation to capture the effects of the band tail states. We also present a compact model that corrects the low-temperature threshold voltage for the band-tail states, Fermi–Dirac statistics, and interface traps. New temperature-dependent mobility and velocity saturation models are accurate down to cryogenic temperature. In addition, we propose that experimentally observed ${I}_{D}$ dependence of subthreshold swing (SS) at cryogenic temperatures is a consequence of the expectedly higher rate of Coulomb scattering of free carriers. [ABSTRACT FROM AUTHOR]

Frequency domain spectroscopy (FDS) technique is widely applied in the condition assessment of the oil-paper system in power transformers. However, the synergistic effect generated by moisture and temperature on the FDS data cannot be analyzed by the existing model since the single independent variable (moisture or temperature) is considered in the construction of the model. To quantify such the synergistic effect, a novel method that utilized for normalizing (or standardizing) the FDS curve is reported based on the theory of the power series and fitting analysis. The present findings reveal that the reported method is capable of predicting the dielectric loss (tanδ) curve under diverse test conditions, in which the average error is less than 7%. The synergistic effect can be also explored by using the extracted feature parameters. The potential application is then proved to make up for the measurement errors during the FDS test, the findings are expected to promote the moisture analysis of the transformer insulation.

The Al/HfOx/AlOy/indium tin oxide (ITO)/polyethylene terephthalate (PET) flexible resistive random access memory (ReRAM) device was fabricated at room temperature to study the effect of AlOy interfacial layer on resistive switching (RS). Incorporating the interfacial layer AlOy improves the cycle-to-cycle, cell-to-cell uniformity and switching resistance ratio (>103). It introduces the oxygen vacancies in HfOx which controls the formation and rupture of filament and plays an important role in improving RS characteristics. The device also maintains the stable switching operation under the flexible condition and at elevated temperature up to 100 °C. The device area and temperature-dependent switching characteristics confirm the Ohmic (hopping) conduction in low-resistance state (LRS) and the space charge-limited conduction (SCLC) in high-resistance state (HRS). [ABSTRACT FROM AUTHOR]

Silicon MEMS resonators are increasingly being adopted for applications in timing and frequency control, as well as precision sensing. It is well established that a key limitation to performance is associated with sensitivity to environmental variables such as temperature and pressure. As a result, technical approaches to address these factors such as vacuum sealing and ovenization of the resonators in a temperature controlled system have been introduced. However, residual sensitivity to such effects can still serve as a significant source of frequency fluctuations and drift in precision devices. This is experimentally demonstrated in this paper for a precision oven-controlled and vacuum-sealed silicon resonators. The frequency fluctuations of oscillators constructed using two separate nearly-identical co-located resonators on the same chip are analysed and differential frequency fluctuations are examined as a means of reducing the impact of common-mode effects such as temperature and pressure. For this configuration, our results show that the mismatch of temperature and pressure coefficients between the resonators ultimately limits the frequency stability. [2020-0395] [ABSTRACT FROM AUTHOR]

This article investigates radiation-induced switching mechanisms, temperature effects, breakdown voltage, sensitive volume, and critical charge definitions for spin-transfer torque magnetic tunnel junctions. The thermal spike model is adopted to estimate the temperature reached during heavy-ion irradiation, and temperature effects are suggested to be responsible for the magnetic properties’ degradation and for upset processes. [ABSTRACT FROM AUTHOR]

We evaluate the temperature effect on the X-ray radiation-induced luminescence (RIL) of Cu- or Ce-single-doped and CuCe-codoped silica glass. Previous investigations showed that these optical materials exhibit interesting dosimetry properties, such as very good detection capabilities and linear response over a large range of dose rate. However, several radiation environments, such as space and particle accelerators, also require a careful assessment of the temperature effect. With this aim, we characterize their RIL efficiency and spectral dependence at several irradiation temperatures. We demonstrate that all the investigated materials present a nonnegligible temperature dependence of the RIL in the range −120 °C to 80 °C, whilst preserving linear dose rate dependence at each irradiation temperature. However, the temperature effect on the RIL signal is still compensable via calibration and temperature monitoring. [ABSTRACT FROM AUTHOR]

Accurate estimation of land surface temperature (LST) is crucial for ecological environment monitoring and climate change studies in mountainous areas. The current LST retrieval algorithms were developed without accounting for the topographic effect, which can only be used to retrieve LST over relatively flat surfaces. Due to the impact of 3-D structure of mountainous surfaces, rugged terrain makes the processes of thermal radiation more complex. In this study, a radiative transfer equation (RTE)-based single-channel algorithm was proposed to retrieve LST with topographic effect correction from the Landsat 8 thermal infrared (TIR) data in mountainous areas. This algorithm accounts for the changes in the thermal radiation components in the TIR RTE caused by the topographic effect. According to the analysis of simulation data, sky-view factor (SVF), atmospheric water vapor content, surface emissivity of target pixel, and average LST of the surrounding terrain have significant influence on the magnitude of the topographic effect. The differences between the LST retrieved without/with topographic effect correction from the Landsat 8 TIR data are related to SVF. The topographic effect should be taken into account in the LST retrieval algorithm when SVF is smaller than 0.7. The largest LST difference of approximately 1 K occurs in the deep valley. The results indicate that LST without topographic effect correction could be overestimated to be as high as 1 K. Due to a lack of in situ LST measurements, the performance of the LST retrieval algorithm in mountainous areas was only evaluated by comparing the brightness temperature (BT) at the top of the atmosphere (TOA) simulated by the DART+MODTRAN model and the TIR RTE over mountainous surfaces at three subregions. There is a good consistency between BT at the TOA simulated by the DART+MODTRAN model and the TIR RTE over mountainous surfaces at the three subregions, with a root-mean-squared error (RMSE) of less than 0.23 K. [ABSTRACT FROM AUTHOR]

A synergistic approach for optimizing devices, circuits, and neural network architectures was used to abate junction-temperature-change-induced performance degradation of an Fe-FinFET-based artificial neural network. We demonstrated that the digital nature of the binarized neural network, with the “0” state programmed deep in the subthreshold and the “1” state in strong inversion, is crucial for robust deep neural network inference. The performance of a purely software-based binary neural network (BNN), with 96.1% accuracy for Modified National Institute of Standards and Technology (MNIST) handwritten digit recognition, was used as a baseline. The Fe-FinFET-based BNN (including device-to-device variation at 300 K) achieved 95.7% inference accuracy on the MNIST dataset. Although substantial inference accuracy degradation with temperature change was observed in a nonbinary neural network, the BNN with optimized Fe-FinFETs as synaptic devices had excellent resistance to temperature change effects, and maintained a minimum inference accuracy of 95.2% within a temperature range of −40 to 125 °C after gate stack and bias optimization. However, reprogramming to adjust device conductance was necessary for temperatures higher than 125 °C. [ABSTRACT FROM AUTHOR]

This work proposes to enlarge the maximum readout distance of battery-free harmonic transponders through a careful Schottky diode selection and a consideration of low-temperature operations. Diode SMS7621 is identified to deliver lower conversion loss (CL) of harmonic transponders based on a diode selection guide. Moreover, an analytical method for studying temperature effects on the transponder CL performance is introduced and derived with satisfactory accuracy. A diplexer inserted in the harmonic transponder design can help reduce the antenna number. To mitigate matching difficulties at both fundamental and second-harmonic frequencies, a third-order diplexer is developed to enhance its bandwidth performance. Experimental verification has shown that low-temperature operations can effectively reduce the CL of the SMS7630-based harmonic transponder, thus increasing its readout distance. Specifically, its maximum readout distance at −40 °C has increased by more than 10%, from 6.4 to 7.1 m, compared with that at +40 °C. A complete harmonic transponder based on SMS7621, with dimensions of 85 mm $\times45$ mm has reached a maximum readout distance of 8 m when the fundamental frequency is 3.5 GHz. [ABSTRACT FROM AUTHOR]

The requirements for accuracy of piezoresistive pressure sensors in modern society are becoming increasingly high. Besides, a wide application range of sensor is required. However, due to the influence of material properties, many piezoresistive pressure sensors have high temperature coefficient, which limits their application temperature range. With the change of ambient temperature, the response characteristic of the sensor has strong nonlinearity. To solve the above-mentioned crucial problems, a dynamic chaos quantum-behaved particle swarm optimization optimized multiple kernel relevance vector machine (DCQPSO-MKRVM) algorithm is presented in this article. First, a basic theory of temperature effect is given and a new idea of temperature compensation is proposed. Second, the multi-kernel relevance vector machine (MKRVM) is adopted to estimate the bias values of input pressure. Through heterogeneous kernel learning method, the kernels of MKRVM maintain diversity to obtain higher estimation accuracy. Third, dynamic chaos quantum-behaved particle swarm optimization (DCQPSO) is employed to optimize the optimal sparse weights of kernel functions in MKRVM. Moreover, the dynamic parameter is applied for the boundary of chaos search between original quantum-behaved particle swarm optimization (QPSO) swarm and the chaos swarm. The experimental result indicates the complex nonlinear relationship of temperature effect, and the method proposed in this article can effectively and accurately estimate the bias of input pressure fast to achieve temperature compensation goal. The mean relative accuracy (MRA) of estimation results achieves 99.5%. It proves that the method proposed in this article is applicable and effective for industrial applications. [ABSTRACT FROM AUTHOR]

Stability is one of the most important characteristics of the potentiometric urea biosensors; however, it has rarely been discussed in previous literature. In this article, the stability of the potentiometric urea biosensor based on the urease-Ag NPs/RuO2 sensing film was studied. Using the voltage–time ($V$ – $T$) measurement system, the stability was verified by analyzing the biosensor’s reproducibility, repeatability, long-term measurement, and effect of temperature. Based on the results of this study, the proposed potentiometric urea biosensor had good reproducibility [relative standard deviation (RSD) was 2.23%] and repeatability (RSD was 1.16%). The urease-Ag NPs/RuO2 sensing film still has 90% initial sensitivity after 15 days of storage at room temperature. Moreover, the proposed urea biosensor was integrated into the microfluidic system and the remote measurement system. The sensing characteristics of the potentiometric urea biosensor under different flow rates (1.4–7.0 $\mu \text{L}$ /min, 0–30 $\mu \text{L}$ /min) were studied. In the remote measurement, the average sensitivity was 45.75 mV/decade and the linearity was 0.986. [ABSTRACT FROM AUTHOR]