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The shore power cable is directly connected between the ship and the shore. Affected by direct sunlight, sea wind and tide, the shore power cable’s insulation has aged, which has a significant impact on the shore power cable’s service life and current carrying capability. In order to investigate the effects of wind speed, water flow velocity, solar radiation, and ambient temperature on the temperature distribution of shore power cables, the paper builds an electromagnetic-thermal-flow multiphysics simulation model of shore power cable CEU94 - 8.7/10 kV - $3\times 120$ mm2. Each layer of the model takes into account parameters such as thermal conductivity and electrical conductivity of the material and is based on the characteristics of the finite element method to ensure accurate calculation of the temperature distribution. Meanwhile, the boundary conditions such as wind speed and water flow velocity are based on meteorological data and water current measurements of the actual harbor to ensure the technical rationality of the model. The findings demonstrate that the conductor temperature varies in a linear fashion with the surrounding temperature. There is a 10°C increase in the ambient temperature and an 11.66°C increase in the conductor temperature; When the wind speed increases from still to 10 m/s, the maximum conductor temperature decreases by 13.84°C; When the shore power cable is laid in the air, the decrease in temperature is within 2°C when the water speed is 10 m/s, and the decrease in temperature is within 15°C when the wind speed is 10 m/s. When laid in water, the temperature stabilizes with the flow velocity, and the temperature of laying in water is about 5.5°C lower than that of laying in air; In extremely hot summer weather, the shore power cable’s maximum conductor temperature is 117.6°C.

Optimizing temperature distribution is one of the crucial tasks in induction heating technology, especially, for small devices with constraints on compactness, efficiency, and cost. The optimization solely using coil shape parameters, referred to as ‘traditional coil design’, cannot provide a satisfactory solution with highly limited structural constraints of lateral or vertical size. A multi-coil system where each set of coils is fed by multiple inverters enables control of the magnitude and phase of exciting currents, providing an alternative approach to enhance the design flexibility. However, additional inverters increase both the volume of a driving circuit and the cost of products, so this approach has a risk of reducing applicability to personal electronics. This article proposes a dual coil system, consisting of primary and secondary coils, to enhance the flexibility for temperature distribution optimization. The impact of primary and secondary coil currents on heat source distribution and efficiency are analyzed, and an equivalent circuit model representing both coils and a workpiece is introduced to provide the main concept of the proposed dual coil system. The effect of circuit parameters on resonance characteristics of the dual coil system are studied for a sensitivity analysis of design parameters. Finally, the optimization flow is proposed and applied to a case study model to demonstrate its superiority compared to the traditional coil design. Potential challenges are discussed to provide insights for further model development.

Several studies have demonstrated that the urban heat island (UHI) impact is significantly influenced by changes in urban land cover (LC). In this study, we examined the dynamic change in LC in Shijiazhuang city and its impact on UHI intensity using multisource data, including landsat and LC data. The results showed that 1) the 15-year span exhibited a substantial growth in built-up area from 14.541% to 19.718%, whereas cropland and grassland dropped by 3.342% and 3.625%, respectively. 2) The mean land surface temperature (LST) in the study area increased significantly. From a point-to-plane distribution, the high-temperature zone (>32 °C) grew, and the direction of growth was consistent with urbanization. 3) The average temperature of the barren areas was the highest, followed by the built-up areas. 4) The normalized difference vegetation index and LST have a strong negative association, showing that LST rises with vegetation loss. Our research results provide a scientific basis for deeper understanding of the mechanisms underlying UHI creation, as well as for developing logical land use strategies and evaluating the effects of urbanization on local climates. [ABSTRACT FROM AUTHOR]

One of the most important parts of semiconductor etch tools is the electrostatic chuck (ESC), which ensures secure wafer holding during fabrication and uniform temperature distribution from center to perimeter of the wafer during plasma etching. In this study, we investigated the thermal and electrical analysis of the ESC to ensure the temperature uniformity of the wafer via analytical multi-physics simulation including backside gas (BSG) flow between the wafer and ESC surface while the high voltage direct current (HVDC) power was applied in the ESC. We devised a bipolar-Coulomb type ESC and compared experimental data with theoretical and computational results. The chucking pressure along the HVDC magnitudes from 500 to 1000 V was investigated through 1D electric circuit and 2D simulation using ANSYS Maxwell. And we investigated the temperature change of the wafer when the BSG pressure changes from 0 to 15 Torr through 1D thermal circuit and 3D simulation using ANSYS Fluent. The 1D equivalent electric circuit showed the same trend with an error rate of 6.94% with 2D simulation and 58.75% with an experiment on average. The 1D equivalent thermal circuit also showed the same trend with an error rate of 0.44% with 3D simulation and 1.52% with an experiment on average. [ABSTRACT FROM AUTHOR]

The ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) onboard the International Space Station (ISS) provides standard land surface temperature (LST) products to meet community concerns on water stress and evapotranspiration. In 2019, an anomaly on the mass storage unit (MSU) changed the data acquisition mode of ECOSTRESS to a direct streaming one, eliminating three bands centered at 1.60, 8.29, and $9.20~\mu \text{m}$. This letter analyzes the feasibility of retrieving LST from ECOSTRESS data using split-window (SW) techniques which need only two thermal infrared (TIR) bands to serve as an alternative to produce LST products. Three different spilt-window algorithms have been developed and analyzed for all possible TIR band combinations using the simulated top-of-atmosphere (TOA) radiance dataset. Besides, the selected SW algorithms were validated using the intercomparison method with ECOSTRESS LST product data and the temperature-based method with surface radiation budget (SURFRAD) ground-based measurements. The result showed that SW algorithms provided higher accuracies than the temperature-emissivity separation (TES) algorithm, with the main advantage that the atmospheric profile data is not demanded prior. [ABSTRACT FROM AUTHOR]

Rich datasets related to the Earth have been obtained because of the rapid development of Earth observation technologies. A broad range of prior research has investigated how to obtain the correlation relationships of relevant features from a large number of data containing spatio-temporal information, which is also the technical basis for big data analysis. Based on the dynamic time warping (DTW) algorithm, this research proposes a correlation analysis method of time series data and applies it to the correlation analysis between the time series features of the surface temperature and melting area of the Antarctic ice sheet. The results show that our method based on the DTW algorithm can effectively distinguish the change details of the nonlinear time series. The correlation coefficients between these two highly correlated factors computed by our method are higher than Pearson’s correlation coefficients by more than 0.2 almost in all study areas where data are available. In summary, the method proposed in this study provides a new feasible way for the correlation study of time series data. It outperforms than traditional correlation coefficients such as Pearson’s correlation coefficient in some fields, specifically when complex nonlinear time series data with certain periodicity are used. [ABSTRACT FROM AUTHOR]

The lunar surface temperature (LST) is one of the important thermophysical parameters of the Moon, which helps to study the radiative properties of the lunar surface. Thermal infrared emission spectra are sensitive to the thermophysical properties of the lunar surface material, and the emissivity data can be used for lunar surface composition inversion. In the past, humans have conducted hundreds of lunar exploration missions, but only a small number have been conducted in the infrared band, and typical examples include the Apollo program and the Diviner lunar radiometer experiment of the LRO satellite. Only part of the lunar surface has been explored by these missions. Sustainable Development Goals Satellite-1 (SDGSAT-1) carries out a complete observation of the lunar surface in three infrared wavelength bands (B1: 8– $10.5~\mu \text{m}$ , B2: 10.3– $11.3~\mu \text{m}$ , and B3: 11.5– $12.5~\mu \text{m}$) by its thermal imager spectrometer as part of its mission. In this study, the temperature-emissivity separation (TES) algorithm is used to retrieve the LST and calculate the thermal infrared band emissivity using the radiometric data obtained by SDGSAT-1 thermal imager spectrometer, and the temperature distribution of full-disk Moon and the emissivity distribution of three bands are also mapped. The temperature retrieval error is verified less than 1 K. [ABSTRACT FROM AUTHOR]

The ventilation structure affects the internal wind road and air distribution of the motor directly, and then has a great influence on motor heat dissipation. Focusing on the 5000kW 10kV high-power motor, this paper establishes a numerical analysis model which has been validated by experiment. Based on the established numerical model, the flow field and temperature field inside the motor under the conditions of variable ambient temperature and variable inlet air velocity are analyzed. The finding demonstrates that the maximum temperature and average temperature of the stator and rotor of the motor increase with the increase of the ambient temperature, and the increase rate of change is basically unchanged, and that decrease with the increase of the inlet air velocity. When the inlet air velocity increase to a certain value, the maximum temperature and average temperature of the motor stator and rotor decrease relatively slowly. This thesis analyses the motor ventilation cooling system and temperature distribution, and provides a theoretical basis for the optimization of motor ventilation structure.

In a high-power semiconductor power module where multiple chips are populated in parallel, the thermal imbalance problem arises. In this article, the next-generation standard high-voltage insulated-gate bipolar transistor module for high-speed railcar traction is investigated to characterize the internal thermal imbalance among paralleling chips and evaluate the impact on temperature distribution in field application. The former is accomplished by a new test algorithm with a purposely designed module sample, while the latter is achieved via an advanced electro-thermal simulation from chip level to system level. The experimentally verified thermal network among paralleling chips reveals the multiple reasons for the thermal imbalance. A comparison between the simulation and experimental results regarding the paralleling chips’ power-cycling scenario helps to confirm the effectiveness of the chip model, the thermal network, and the electro-thermal simulation approach. A further electro-thermal simulation shows that the module internal thermal imbalance can lead to significant junction temperature discrepancy among paralleling chips in traction inverter applications, which should be taken into consideration for the long-term reliability assessment. [ABSTRACT FROM AUTHOR]

Insufficient current capability is the most serious problem faced by power electronic devices in hybrid dc circuit breaker (HCB), where the junction temperature rise is the main restriction. This letter proposes a novel performance enhancement method for power electronic switch in HCB based on partial precooling. By applying thermoelectric cooling technology, the temperature of power electronic devices and their surrounding region can be reduced in advance in the steady state of the HCB, allowing the devices to achieve superior current performance. Then, a 4.5 kV power electronic switch module prototype with a low-cost integrated precooling unit was developed, which can provide a temperature drop of 15 °C for the power electronic device within, resulting in approximately 10% improvement in current performance. [ABSTRACT FROM AUTHOR]

In order to accurately determine the electrostatics of Ultra-Thin-Body (UTB) devices, the semi-empirical tight-binding (TB) approach is widely used for calculating the channel thickness dependent band structure of any material at those temperatures where TB parameters are available (generally defined at 0 K and 300 K). In this work, we analyze the variation of band structure for Si, Ge, and GaAs over different channel thicknesses at 0 K and 300 K, and show that the band curvature at the band minima remains unchanged with temperature, while the band gap changes significantly and affects the channel electrostatics. Based on this finding, we propose an approach to simulate the electrostatics of UTB devices, at any temperature between 0 K and 300 K, using the band structure obtained at 0 K, along with a suitable channel thickness and temperature-dependent band gap correction. From the results obtained for the channel charge density, we show good agreement with band structure based simulation results, at 300 K, over a wide range of channel thicknesses, for Si, Ge, and GaAs, while also showing good agreement with TCAD simulation results, at a typical intermediate temperature of 150 K, thus highlighting the accuracy, simplicity and wide applicability of the proposed approach. [ABSTRACT FROM AUTHOR]

Sensitivity (${S}$) and drive mode are crucial issues for the vertical metal-oxide-semiconductor (MOS) type diode applied in temperature sensing. In this study, experimentally, we indicated that the ${S}$ values of the ${\mathrm {Ni}}_{(\text {50 nm})}$ - ${\mathrm {Au}}_{(\text {100 nm})}$ /Ga2O3/ ${p}$ -Si vertical MOS type diode, using the measured capacitance–voltage (${C}_{\text {m}}$ – ${V}$) outputs, are obtained with a novel drive mode. We applied the constant capacitance mode to drive the silicon thermo-diodes as well as constant current mode, and constant voltage mode, which are known as two different methods in the literature. Meanwhile, the ${S}$ value is 21.2 mV/K at 1 nF. This value is the highest value proven in the literature excepting the cryogenic temperature region, and near room temperature. This study provided an original structure for the silicon thermo-diodes and a novel way to drive them. [ABSTRACT FROM AUTHOR]

To avoid overheating of 3-D network-on-chip (NoC)-based multicore systems, many researchers have used dynamic thermal management (DTM) techniques, which need embedded thermal sensors to provide accurate temperature information. However, only a few sensors can be embedded due to the limited hardware cost. So, it is crucial to find an appropriate way to allocate number-limited sensors at design time and reconstruct full-chip temperature accurately using the limited temperature information. However, the relationship between the non-sensor-allocated nodes and the sensor-allocated nodes modeled by the existing methods has a deviation from the actuality, which leads to an inaccurate temperature reconstruction. Another problem is that the existing methods depend highly on the training data. The estimation error can be significant when the running application’s traffic characteristic differs from the one in the offline phase. This article presents a sensor allocation method based on the cores’ spatial correlation, which is not dependent on the training data. Our allocation method contains two stages: 1) using our nearest-neighbor-based initialization algorithm to allocate sensors preliminarily and 2) using genetic algorithm (GA) to optimize the initial allocation. Besides, we use artificial neural network (ANN) to reconstruct the full-chip temperature. Compared with the state-of-the-art methods, our method can improve the average accuracy of the estimated temperature under different scenarios by 17.60%–88.63%. What is more, our approach has high flexibility and can adapt to different application scenarios with high accuracy with only one offline training. [ABSTRACT FROM AUTHOR]

Power budget is an important power constraint provided to guarantee the thermal reliability of an integrated system. In this work, we present DBP, a distributed power budgeting method, for dark silicon many-core systems. In DBP, there are two new techniques proposed to bring accurate and optimized power budgets in a distributed way. First, a distributed active core locating technique is developed to find an active core distribution that leads to a high-power budget. Second, a distributed power budget computing technique is introduced which computes the power budget for each active core accurately. Experiments show DBP outperforms the state-of-the-art power budgeting methods’ thermal safe power (TSP) and greedy dynamic power (GDP) on many-core dark silicon systems by providing a high and accurate power budget with low overhead and good scalability. [ABSTRACT FROM AUTHOR]

In this article, we present a comprehensive analysis on the thermal response characteristics of the stator winding insulation under static air-gap eccentricity (SAGE) conditions in synchronous generators. Different from previous studies, this article not only takes into account the interactions of both the core-loss-caused heat and the copper-loss-caused heat but also investigates the thermal degrading distribution regularities due to SAGE. The whole work is based on the qualitatively theoretical analysis, the finite-element analysis, and the experimental validation on a nonsalient synchronous generator. The study shows that SAGE will significantly make the temperature rise, resulting in uneven temperature distribution and intensifying the thermal responses, such as the thermal deformations, stresses, and strains, of the insulation. The nose part and the joint between the line winding and the end winding on the smaller air-gap side are the two most dangerous positions. [ABSTRACT FROM AUTHOR]

Temperature sensitive electrical parameters (TSEP) provide an indirect and noninvasive method for on-line junction temperature estimation of power semiconductor devices. It is known that the fundamental of TSEP-based methods is to calibrate the relationship between TSEP and junction temperature in advance. However, the calibration methods in the literature need to open the module, require pretesting, or record the operating data of a converter in the entire power rating range, which are inconvenient in field applications. This article proposes an on-line and noninvasive calibration method by measuring the data at three operating states that are already existed in the regular converter operation. It is achieved by measuring the accessible heatsink/case temperature and TSEP during converter regular operation. The concept, implementation, and error analysis of the proposed method are presented in this article. Experimental verification is given to prove the effectiveness, accuracy, and convenience of the proposed method. [ABSTRACT FROM AUTHOR]

A study is made of the optical inline-Sagnac interferometer current sensor/transducer with active phase modulation and with spun polarization maintaining fiber. A brief review of the common sensor types is made to give context to the discussion of the optical inline-Sagnac current sensor theory. A new discussion is made of the limitations of the optical inline-Sagnac interferometer current sensor caused by the spun polarization maintaining fiber, the polarizing fiber design, and the temperature effects of each type of fiber. These combined temperature effects limit the sensor to a practical scale factor temperature sensitivity range of about 80 to 200 ppm/°C. The fiber component optical-wavelength effects require a broad-band light source to have a wavelength stability of <0.65 nm to achieve a ±0.1% sensor scale factor stability. The opto-mechanical effects from available spun polarization maintaining fibers limit the measurement head to diameters >30 mm. The transit-time of the light through the sensor is the ultimate bandwidth limit for the device. However, most practical sensors have −3 dB bandwidths >20 kHz. In utility applications the isolation of the sensor to nearby currents is estimated to be −96 dB. [ABSTRACT FROM AUTHOR]

Surface charge accumulation on an insulating spacer is a critical issue that causes electric field distortion and flashover voltage reduction in DC-GIS. In the operating environment, high-voltage electrode is heated by Joule heat, and the surface charge accumulation is strongly affected by the temperature. This study reports the temperature dependence of surface charge accumulation on DC-GIS insulating spacer and its impact on electric field distortion. Surface charge density distribution is measured on a downsized epoxy spacer under isothermal conditions at room temperature, 40 °C, and 70 °C. Special care is taken to realize a low-moisture and low-dust environment. We obtain the saturation tendency of homo-charge accumulation with less random charges and its temperature dependence. Homo-charge accumulation develops more rapidly and more extensively on the spacer at the higher temperatures. Our results indicate that the surface charge accumulation cannot be explained by a conventional resistive field calculation, and that an explanation based on charge trapping is reasonable. They also show that the homo-charge accumulation significantly contributes to the electric field enhancement after the polarity reversal in our experimental system, especially at high temperatures. [ABSTRACT FROM AUTHOR]

Turn-off failure under clamped inductive load, is one of the most concerns in insulated gate bipolar transistor (IGBT) chips. Besides, this turn-off failure can be attributed to two causes, i.e., the dynamic latch-up and the secondary breakdown. Despite great simulation work investigated previously, the experimental research should be further focused. Up to now, the typical features and differences for these two turn-off failures still remain unclear. In this article, two failures’ waveforms are first compared in experiment. Moreover, their internal current, electric field, and temperature distributions are compared by simulation in detail. Then, two different failure features, focusing on the failure cell structures, are summarized from the scanning electron microscope (SEM) results for the first time. The marked signatures of these failures, such as the current filament path and the mixture region, are further analyzed in this article. According to the SEM results, the lateral and vertical current paths can be observed in dynamic latch-up chip and secondary breakdown chip, respectively. These failure signatures in waveforms and SEM results can contribute to the distinguished method to the failure causes in IGBT device, and enhance the chip's performance more effectively. [ABSTRACT FROM AUTHOR]

Power electronics converters operating at elevated temperature usually have degraded performance, such as reduced efficiency, lower noise immunity, and decreased system reliability, compared to those operating at room temperature. Nevertheless, harsh-environment applications, such as deep earth drilling, automotive, avionics, and space exploration, have been utilizing converters in high-temperature environments and are continuously pushing the temperature limits higher and higher with the advances in device technologies and converter design methodologies. This article starts with a literature study to identify the temperature dependence and the temperature limits of individual components. Then, published works about high-temperature converters are examined. Their selection of components is compared. Experimental results are analyzed to reflect on the efficacy of different component selections. Finally, since the latest published high-temperature converter was developed more than five years ago, a 1-kV input, 520-V output, 1-kW, $150$ °C-ambient-temperature-rated dc–dc converter is designed with state-of-the-art devices. Based on the literature review, and the test of the $150$ °C prototype, the main challenges of designing high-temperature power electronics converters are identified and concluded to be time-consuming, difficult, and expensive characterization of components, lack of accurate and computationally efficient models of converters, and optimizing component selection within short development time. [ABSTRACT FROM AUTHOR]

The natural gas tightly correlates with our everyday life. However, driven by gray incomes, some users are prone to stealing gas by refitting the equipment without permission. Especially for the boiler room users in winter, this phenomenon appears more rampant. Traditional gas-theft detection methods highly rely on the on-site inspection, where exists ineffective and randomness. With the rapidly deployed IoT sensors, we can collect real-time gas consumption data to analyze users’ behavior patterns, where the gas-theft suspects could be discovered early and accurately. In this paper, we propose a data-driven approach, named SVOC, to detect gas-theft suspects among boiler room users. Our approach consists of a scenario-based data quality detection algorithm, a deformation-based normality detection algorithm, and an One-Class Support Vector Machine (OCSVM) based anomaly detection algorithm. Specifically, considering the temporal proximity between the gas consumption and the outdoor temperature, the normality detection algorithm adopts a similarity-based deformation correlation to detect normal boiler room users out of abnormal ones. Then, we employ OCSVM as the anomaly detection algorithm to capture various features across multiple data sources, aiming to distinguish gas-theft suspects from the remaining irregular users. Here, the detected normal and abnormal users are fed into the OCSVM for training and prediction, respectively, which can overcome the label scarcity problem. We conduct extensive experiments on a real-world dataset during one heating season. The results demonstrate distinct advantages of our approach over various baselines. We have developed a real-time system on the cloud, providing daily gas-theft suspects for gas companies. [ABSTRACT FROM AUTHOR]

This article presents a BJT-based CMOS temperature sensor with a wide sensing range from −50 °C to 180 °C. To effectively relax the sensor resolution requirement and conversion time over the entire temperature range to improve energy efficiency, we introduce a nonlinear subranging readout scheme together with double sampling to achieve dynamic reconfiguration of the sensor readout according to the ambient temperature. We further reduce the sensor power at high temperature by devoting the $\beta $ -cancellation circuit only for BJT biasing while applying a temperature-independent bias current for the other sensor building blocks. Implemented in 0.18- $\mu \text{m}$ CMOS with four-wire connections and switch-leakage compensation based on small BJTs, the proposed sensor chip prototype achieves a high resolution-FoM of 7.2 pJ $\cdot \text{K}^{{2}}$ at 150 °C, while featuring a small sensing error of ±0.45 °C under a 1.5-V supply. [ABSTRACT FROM AUTHOR]

This article presents a versatile shunt-based current sensor for battery management applications. It digitizes the current-induced voltage drop across an external shunt resistor with the help of a 2nd-order delta-sigma ($\Delta \Sigma $) ADC, whose summing node is implemented as a low-noise capacitively coupled amplifier. To compensate for the shunt’s finite temperature coefficient (TC), the TC of the ADC on-chip voltage reference can be tuned. As a result, the sensor maintains high accuracy when used with low-cost high TC shunts, such as PCB traces, as well as with more expensive low TC shunts, such as metal-alloy resistors. Optimal gain flatness over temperature is achieved by a two-current room-temperature TC tuning scheme, which exploits the shunt’s self-heating at high current levels. Fabricated in a standard 0.18- $\mu \text{m}$ CMOS process, the current sensor occupies 0.36 mm2 and draws 265 $\mu \text{A}$ from a 1.8-V supply. Over the industrial temperature range (−40 °C to 85 °C) and a ±25-A current range, it achieves the state-of-the-art gain error (±0.25%) with both PCB (1.6 $\text{m}\Omega $) and metal-alloy (2 $\text{m}\Omega $) shunts. With these shunts, it achieves 5.3-mA/4.3-mA (rms) resolution in a 10-kHz bandwidth. [ABSTRACT FROM AUTHOR]

Ventilation cooling design is one of the key technologies during the design of large hydrogenerator. With the increase of hydrogenerator capacity, the overheating problem of rotor region become more and more serious. In this paper, a 250 MW hydrogenerator is analyzed. The transient electromagnetic field of the hydrogenerator is calculated. The losses (heat sources) of rotor components in the rotor region of the hydrogenerator are determined. Three-dimensional fluid and thermal coupled mathematic model of the hydrogenerator rotor region is established. The rotor rotation of the hydrogenerator is considered. The distribution of complex fluid velocity in the rotor region is calculated using the finite volume method. The influence of fluid velocity in the different directions on the temperature of the rotor excitation winding is studied under the different flow rates in the rotor region. The surface heat-transfer coefficient distribution of the rotor components is determined. The temperature distribution of the rotor excitation winding, rotor pole body, rotor press plate, rotor damping bar, and rotor end ring is obtained. The calculated temperature results match well with test values. These provide an important reference for the rotor structural design and optimization of larger hydrogenerator.

Verification is a critical process in the development of engineered systems. Through verification, engineers gain confidence in the correct functionality of the system before it is deployed into operation. Traditionally, verification strategies are fixed at the beginning of the system’s development and verification activities (VAs) are executed as the development progresses. Such an approach appears to give inferior results as the selection of the VAs does not leverage information gained through the system’s development process. In contrast, a set-based design (SBD) approach to verification, where VAs are dynamically selected as the system’s development progresses, has been shown to provide superior results. However, its application under realistic engineering scenarios remains unproven due to the large size of the verification tradespace. In this work, we propose a parallel tempering approach (PTA) to efficiently explore the verification tradespace. First, we formulate an exploration of the verification tradespace as a tree search problem. Second, we design a parallel tempering (PT) algorithm by simulating several replicas of the verification process at different temperatures to obtain a near-optimal result. Third, We apply the PT algorithm to all possible verification states to dynamically identify near-optimal results. The effectiveness of the proposed PTA is evaluated on a partial model of a notional satellite optical instrument. [ABSTRACT FROM AUTHOR]

This article studies the influence of fiber Bragg grating (FBG) head length on insulated gate bipolar transistor (IGBT) direct on-chip thermal sensing performance of FBG sensors. To this end, the surface of a commercial IGBT chip is thermally simulated and experimentally characterized. Uniform FBG sensors with three head sizes are then tested in two promising thermal sensing locations. The study has found that the large thermal gradients in this application create an additional constraint when using longer head lengths. A distortion in the reflected spectrum of the 5-mm FBG sensor is used to illustrate the underlying physical effect, which causes this limitation for IGBT junction temperature measurement. This additionally affects the length of head sizes providing accurate temperature readings of the IGBT surface hotspots, and significantly, this limit is location-dependent in a given IGBT geometry. [ABSTRACT FROM AUTHOR]

Excellent high-temperature performance (298–523 K) of the 4H-SiC n-p-n bipolar phototransistor detector (PTD) was explored. It was fabricated using the 4H-SiC epitaxial wafer grown by high-temperature chemical vapor deposition (HTCVD). The static and dynamic properties of the device were tested and analyzed. The results show that the device still has an optical gain of up to 103, a wide linear response range, and good repeatability at the high temperatures up to 523 K under a 3-V bias with a wavelength of 360 nm. The temperature coefficient of the optical gain is extracted, the value of which is 1.02/K. Although the response time of the device increases with the temperature, the increased percentage in responsivity is significantly greater than that of the response time. The results provide an important experimental reference for the application of high-temperature detection and suggest that the PTD has the potential to be used in ultraviolet (UV) detecting systems at high temperatures. [ABSTRACT FROM AUTHOR]

As the operating temperature of the motor increases, the material properties will be seriously affected, such as soft magnetic materials, hard magnetic materials, and winding insulation properties. For high-speed permanent magnet motors, the higher loss density and smaller heat dissipation area make the impact of temperature more serious. However, according to the test standard, the magnetic properties are usually measured at room temperature, ignoring the effect of temperature. To accurately design magnetic devices, it is necessary to understand the behavior of magnetic materials at different temperatures. In this article, a new high-speed permanent magnet claw-pole motor with soft magnetic composite for a wide temperature range is proposed. The design process mainly includes the calculation and analysis of material temperature characteristics, bearing support, topological structure, rotor stress calculation, and so on. Finally, a prototype is manufactured and tested to verify the design process. [ABSTRACT FROM AUTHOR]

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]

A synchronous condenser (SC) can provide the dynamic reactive power for the ultra-high-voltage direct current converter station during the system voltage drop caused by the single-phase short-circuit fault, which is one of the prevalent faults. However, the single-phase short-circuit fault can also result in the increase of the rotor loss and temperature and thus restrict the transient operating ability of the SC. A key factor that affects the rotor loss and temperature rise is the material of the rotor slot wedges. For a 300-MVar SC with the rotor slot wedges made of the aluminum, beryllium bronze, and stainless steel, the rotor loss and temperature distribution under the single-phase short-circuit are calculated by coupling the electromagnetic and temperature field models of the SC with the models of the power grid. The variations of the rotor losses along with the rotor slot wedge conductivity are revealed. The rotor regions, where the highest temperature rise appears, are obtained. According to the maximum permissible temperature of the rotor material, the transient operating ability of the SC withstanding the single-phase short-circuit fault is obtained. This article can provide the theoretic basis for improving the transient operating ability of the SC. [ABSTRACT FROM AUTHOR]

The piezoelectric actuator is a kind of actuation device that acts through the inverse piezoelectric effect. Due to advantages of high precision, low power consumption, compact size, and flexible structure design, they have a wide range of applications in optics, robotics, microelectromechanical systems, and so on. Piezoelectric materials are the core materials for piezoelectric actuators. In this review, recent developments in high-performance piezoelectric materials (HPMs) are introduced, including relaxor ferroelectric crystals, textured ceramics, piezoelectric metamaterials, and so on. The advances of piezoelectric actuators are introduced in this review based on the developments of those piezoelectric materials, where the relationship between the figure of merits of materials and the performance of actuators is also discussed. Finally, we present outlooks and challenges for piezoelectric materials and actuators. [ABSTRACT FROM AUTHOR]

As the complexity of the multicore system grows, the large workload diversity results in serious thermal problems. In a practical way, the number of placed thermal sensors is usually limited due to the manufacturing cost. In recent years, the compressive sensing (CS) theory is proven as an efficient way to reconstruct the original signal by using fewer sampling data. However, due to the high computational complexity during the signal reconstruction, the CS theory is not appropriate to apply to the real-time temperature monitoring in the current multicore system. In this article, we propose a grid-based sensor placement approach to placement the number-limited thermal sensors on the target multicore system. On the other hand, we adopt the matrix inversion bypass (MIB) property to reduce the computational complexity of two widely used signal reconstruction approaches in CS theory [i.e., the orthogonal matching pursuit (OMP) and stagewise OMP (StOMP)]. Due to the characteristic of random sampling in CS theory, the complexity of thermal sensor placement for multicore systems can be reduced significantly. In addition, the proposed MIB-based temperature reconstruction method helps to satisfy the requirement of real-time temperature estimation. The experimental results show that the proposed approach can reduce 57%–93% average full-system temperature reconstruction error compared with the previous non-CS-based approaches. Besides, we can also reduce 22%–41% computing latency compared with the current CS-based reconstruction algorithm. Due to the MIB-based operation, we can bypass the matrix inversion operation for temperature reconstruction. Therefore, the hardware overhead of the temperature reconstruction unit can be reduced significantly. Compared with the conventional approaches, we can reduce 24%–87% area overhead and improve 50%–220% hardware efficiency. [ABSTRACT FROM AUTHOR]

Conventionalpermanent magnet (PM) machine temperature assessment approaches require physical, material, and loss distribution information. In practice, accurate structural information is rarely available, a lot of thermal parameters can only be calibrated based on extensive experiments, and the determination of various machine losses is also a demanding task. To solve these problems, an online temperature prediction method is proposed in this article. A general mathematical model that describes the relationship between machine temperature and loss variation is derived through analyzing a PM machine three-dimensional lumped parameter thermal network. With distributed sensors, this model can be determined purely from the measured data, which eliminates the need to acquire machine physical and material information. The analyses of loss distribution are also avoided by utilizing two measured temperatures. The evolution of all sensors can be concerned, so the prediction of the time and spatial distribution of temperature can be realized. The proposed method is validated by the experiments processed on a 10-kW PM machine under various working conditions. The influences of key parameters and the comparison with a neural network model are also demonstrated. The results suggest that the proposed method has the advantage of possessing closed-form expression and being computationally efficient. [ABSTRACT FROM AUTHOR]

In this article, the influence of thermal coupling in power modules on lifetime under power cycling test (PCT) is investigated. In a full-bridge power module for electric vehicle application, the thermal coupling is strong due to high power density and causes lateral temperature difference. In PCT, at the same maximum junction temperature Tvjmax and temperature swing ΔTvj, the influence of thermal coupling on lifetime and failure mode is investigated. The root cause of why thermal coupling influences lifetime and the failure mode is discussed by finite-element analysis. Transient thermal impedance is used to calibrate the simulation model. The Influence of thermal coupling on chip surface and solder layer temperature distribution is analyzed under the same test conditions. Furthermore, two parameters are extracted from the temperature distribution of chip surface as flags of failure mode determination. Finally, taking thermal coupling into account, combined with direct copper bonding structure, an improved layout is recommended in terms of lifetime. [ABSTRACT FROM AUTHOR]

Based on thermoelectric analogy method, a thermal network model coupled with electromagnetic loss is presented. According to the actual structure of dry-type transformer windings, an accurate thermal network is established. Considering the distribution characteristics of heat source along the cooling ducts inside the dry-type transformer, the thermal parameters such as heat flux and convective heat transfer coefficients are calculated by finite element method (FEM) analysis and computational fluid dynamics (CFD). Based on the temperature rise experiment, the hottest spot located at the top of the outmost high-voltage (HV) winding is 151.8 °C, which verified the correctness of thermal network model. [ABSTRACT FROM AUTHOR]

Recently, artificial neurons have attracted much attention due to their excellent energy efficiency and scalability. However, there are still few reports on the regulation of the performance of artificial neuron based on single device. In the letter, we present an artificial neuron device based on Ag/TaOx/Si that not only has excellent turn-on and turn-off performance, but also exhibits sustained stability under multiple cycle tests. Moreover, the Integrate -and-Fire (IF) neuron model is successfully simulated at room temperature. More importantly, we find that an increase of temperature could reduce the threshold voltage and reset voltage of neurons, improve the probability of neuronal firing, and promote the transformation of neurons from nonvolatile to volatile. This work provides an effective method for regulating artificial neurons and has important implications for studying information transfer in biology and adapting complex computations in a memory computing framework. [ABSTRACT FROM AUTHOR]

${p}$ -channel GaN field-effect transistors (FETs) with a SiNx/GaON gate stack have been demonstrated with enhanced stability within a wide range of voltage bias and temperature. In this letter, the gate leakage characteristics and reliability of this unconventional staggered gate stack are investigated. At relatively low gate voltages, the gate current is suppressed owing to the buried-channel structure and the presence of GaON that presents an effective hole barrier. With more negative gate biases, the gate leakage was found to be dominated by the transport of holes that spillover from the ${p}$ -channel through the SiNx via Poole-Frenkel emission. Based on this gate leakage mechanism at large gate bias, $\sqrt {{\mathrm {E}}} $ model was used for gate lifetime prediction. The maximum applicable ON-state gate voltage of −7.3 V is obtained for a 10-year lifetime with a 1% gate failure rate. [ABSTRACT FROM AUTHOR]

The presence of multiple cores in modern multicore architectures makes thermal management and temperature estimation a really challenging task for enhancing reliability and lifespan. Due to the presence of many cores, the core/tile spacing needs to be optimized in order to enhance the thermal coupling between interconnect routing blocks and active tiles. In addition, the tiles activity patterns under partial workload conditions significantly affect the maximum on-chip temperature which results in nonuniform temperature distribution. This is due to poor thermal coupling between neighboring tiles owing to the decrease in spacing between cores. In this article, we investigate the thermal performance analysis of a 256-core (i.e., 64 tiles) Mempool reduced instruction set computer (RISC) V-based architecture considering the impact of inter tiles spacing. Simulation results reveal that lateral heat spreading predominantly affects the thermal performance in multicore architectures under partial workload conditions. We also optimize the thermal performance with different tiles activity pattern. Simulation results reveal that both the maximum on-chip temperature and lateral heat spreading are improved for specific tiles activity patterns. Also the thermal performance analysis considering the “tile-insite effect” reveals that there is little impact on on-chip maximum temperature ($T_{\text {max}}$), but the on-chip thermal gradient ($\Delta T$) and the thermal profile pattern are predominantly affected. Finally, the effect of the secondary heat path toward printed circuit board (PCB) is studied in this work. [ABSTRACT FROM AUTHOR]

This article presents a bounded model checking (BMC)-based temperature-aware software-based self-testing (SBST) technique to test worst case delay faults within the highest temperature range. The BMC-based SBST method first defines the sequential constraint. It develops a sequentially constrained automatic test pattern generation (ATPG) to ensure that the generated delay test patterns can emerge in functional mode. It then uses the processor’s multiple-level information to reduce the model complexity, avoid aborts due to time-outs during the BMC process, and generate test programs automatically. A temperature-aware SBST method has then been developed to ensure that the test temperature is within the specified range and test the worst case delays under high temperature. Experimental results demonstrate that the proposed technique achieves an extremely high coverage for delay faults and effectively avoids yield loss caused by the overtesting problem. Its test quality also outperforms that of the existing methods. The generated SBST programs are successful and efficient in testing worst case delay faults under high temperature. [ABSTRACT FROM AUTHOR]

We have demonstrated a wide radiation temperature measurement by using a single-photon avalanche diode (SPAD) image array that is analogous to a silicon photomultiplier with a time-gating technique and an adjustable summed output. The detection temperature window ranging from 280 °C to 1050 °C can be achieved with a noise equivalent temperature difference (NETD) value of below 1 °C. The thermal image with a high detection rate up to 1680 Hz is obtained at the same detection temperature as a commercial CMOS thermal camera. We further demonstrate a thermal image with a spatial resolution of $80~\mu \text{m}$. [ABSTRACT FROM AUTHOR]

Conventional thermal flow sensors require samples to be heated; however, the temperature rise of the measuring tools limits their use in biological applications. To address this limitation, in this study, we propose a thermal flow sensor with a bidirectional thermal reference. We fabricated an integrated calorimetric and hot-film thermal flow sensor with a bidirectional thermal reference using a Peltier module to produce a thermal distribution that depends on the flow rate. The integrated thermal flow sensors enable high-resolution and wide-range flow rate measurements in a microfluidic device without the use of heating reagents in the cooling measurement mode. In addition, the sensor can be used as a typical heating thermal flow sensor by inverting the current applied to the Peltier module. Computational fluid dynamics simulations and experiments were performed to evaluate the performance of the integrated sensors in heating and cooling modes. In both modes, the calorimetric sensor measured low flow rates with a resolution of 100 nL/min, whereas the hot-film sensor measured a wide range of flow rates up to 200 $\mu \text{L}$ /min. The proposed sensor expands the use of the thermal flow sensors by switching between the cooling and heating modes according to the sample temperature and maximum temperature limit. [2022-0090] [ABSTRACT FROM AUTHOR]

The objective of the work presented here is to estimate the characteristics of the power balance, i.e., the power and the surface power density that the electric arc brings to silver–tin oxide (Ag–SnO2) electrodes. This work is first based on an experimental study carried out using an IR camera with which we measured the temperature in a zone close to the area impacted by the arc, but not flashed by it. In a second step, the temperature distributions obtained are compared with the results of a numerical model of the electrode heating. The model input parameters are the power $P$ and the surface power density $Q$. Solving this inverse problem thus makes it possible to estimate the values of $P$ and $Q$ leading to measured and calculated heating (temperature distribution) that are as similar as possible. Such a method has been applied for Ag–SnO2 cathodes and anodes and for various intensities of the arc current in a range of 80–200 A. [ABSTRACT FROM AUTHOR]

With the increasing density of flash memory, its service life is declining. As the most important technical index of a flash device, flash retention parameters often need to consume a substantial amount of time to be tested. With a view toward reducing the test period, the most popular method currently is to speedup the retention loss of flash memory at high temperatures. However, since the retention loss of flash memory is the result of a mixture of multiple failure mechanisms, the Arrhenius model with a single apparent activation energy ($E_{aa}$) has significant limitations in calculating the high-temperature acceleration factor for the retention loss of flash memory. In this article, based on a large number of real experiments, we have studied the retention characteristics of the flash memory in high-temperature environments and closely tracked the change of $E_{aa}$ at different temperatures, retention time, and program/erase (P/E) cycle count. The experimental results show that the equivalent acceleration factor (AF) grows rapidly with retention time at the beginning of flash retention and that flash with a high P/E cycle count has a faster AF growth rate. [ABSTRACT FROM AUTHOR]

In this paper, a reduced computational fluid dynamics (CFD) model is proposed for determining the total heat dissipation and the oil temperature distribution of transformer radiators in oil natural air natural (ONAN) cooling mode. In the reduced radiator CFD model, the air flow simulation is replaced with an optimized air heat transfer coefficient (hair) equation. An experimentally verified full radiator CFD model, which includes the air flow simulation, has been introduced as a benchmark model for evaluating the validity of the reduced model. It was found that one ${{\boldsymbol{h}}_{{\boldsymbol{air}}}}$ can provide sufficient accuracy in simulating the air convection effect of transformer radiators. An ${{\boldsymbol{h}}_{{\boldsymbol{air}}}}$ equation was derived through a parametric study using the full radiator CFD model. The performance of the proposed ${{\boldsymbol{h}}_{{\boldsymbol{air}}}}$ equation was compared with the existing empirical equations, and its validities for different insulating liquids and different ambient temperatures were proven by additional CFD modelling. This ${{\boldsymbol{h}}_{{\boldsymbol{air}}}}$ equation can be transformed into a dimensionless form to help the radiator design and facilitate the complete-cooling-loop (CCL) based transformer CFD modelling. [ABSTRACT FROM AUTHOR]

Multiple strokes are the main factors affecting the safe and stable operation of power equipment. As the core lightning protection equipment, arresters are also frequently thermally collapsed due to multiple strokes. This paper investigates thermal effects of polymer-housed metal-oxide surge arrester (PMOSA) under multiple strokes. The comparative experiments of PMOSA lightning impulse are carried out through multiple strokes of experiment platform, including continuous lightning stroke and multiple strokes. Furthermore, the temperature distribution of the housing surface is obtained by infrared imager for thermal effect analysis. Subsequently, some typical DC parameters are tested to explore the association of impulse aging and thermal effects of the arrester under multiple strokes. Finally, a thermal-electric coupling model (TECM) is constructed to investigate the influence of some factors on the temperature of PMOSA from the perspective of materials and structure. The research in this paper can provide a theory reference and brief data support for improving the heat dissipation performance of arresters under multiple strokes based on structural optimization design and material modification. [ABSTRACT FROM AUTHOR]

Battery fault diagnosis is crucial for stable, reliable, and safe operation of electric vehicles, especially the thermal runaway early warning. Developing methods for early failure detection and reducing safety risks from failing high energy lithium-ion batteries has become a major challenge for industry. In this article, a real-time early fault diagnosis scheme for lithium-ion batteries is proposed. By applying both the discrete Fréchet distance and local outlier factor to the voltage and temperature data of the battery cell/module that measured in real time, the battery cell that will have thermal runaway is detected before thermal runaway happens. Compared with the widely used single parameter based diagnosis approach, the proposed one considerably improve the reliability of the fault diagnosis and reduce the false diagnosis rate. The effectiveness of the proposed method is validated with the operational data from electric vehicles with/without thermal runaway in daily use. [ABSTRACT FROM AUTHOR]

The real-time monitoring and scientific prewarning of local overheating for electrical equipment and electronic devices are of great significance but remain challenging. Therefore, in this work, a temperature-responsive microcapsule is prepared to endow insulating materials with the ability to thermally sense external temperature fields. Specifically, in the microcapsule/epoxy composites, the epoxy resin served as the polymer matrix was doped with reversible thermochromic microcapsules, acting as a temperature indicator whose color transition temperature is centralized between 45 °C and 55 °C. The test results indicate that the color of the prepared composites can sensitively vary in response to the fluctuations in external ambient temperature, which was illustrated by the behavior of isothermal melting. Further analysis reveals that composites are able to precisely locate multiple tiny overheated areas and present remarkable thermal durability undergoing 480 h of aging at 70 °C. The thermochromic materials designed in this article provide a new technological route for large-scale thermal sensing applications of electrical equipment. [ABSTRACT FROM AUTHOR]

Epoxy resin (EP) is a typical and widely used insulating material for medium-frequency transformers (MFTs). The dielectric loss of EP is one of the key variables in the design and operation of MFT. In this article, six types of epoxy/anhydride systems are prepared, and the dielectric loss of MFT is calculated by finite element method (FEM) analysis based on broadband dielectric spectroscopy measurements. The material dependence of the dielectric loss of MFT is investigated using dielectric spectroscopy and molecular dynamics simulations over a wide temperature and frequency range. The results show that the variation of dielectric loss with output power is attributed to the temperature characteristics of the imaginary part ($\varepsilon ^{\prime \prime }$) of complex permittivity. Compared to the dielectric loss at no-load state, the one at rated power is reduced by 5–10 W. The anhydride hardener containing benzene ring or a methyl substituent has an inhibitory effect on dielectric loss, and the EP cured by methyl nadic anhydride (MeNA) has the lowest dielectric loss (16.2 W) at rated power. The dielectric loss and overload characteristics of MFT are closely related to the $\beta $ -relaxation and $\alpha $ -relaxation of EP, respectively. The acid anhydride curing agent containing benzene ring or a methyl substituent reduces the temperature corresponding to the $\beta $ -relaxation peak by more than 50 °C compared to the one without. The increased rigidity of the chain segment of EP makes the $\beta $ -relaxation move to the low-temperature side, which is beneficial to suppress the dielectric loss. This article not only serves as a bridge among dielectric loss of MFT, dielectric spectroscopy, and molecular structure of EP but also lays a solid foundation for the selection of insulating materials for MFT. [ABSTRACT FROM AUTHOR]

The Industry 4.0 (I4.0) is a paradigm settled down by the introduction of the Internet of things (IoT) into the production and manufacturing environment. I4.0 promotes the connection of physical items such as sensors, devices, and enterprise assets, to each other and to the Internet. The information that flows through these items is vital because it serves to make relevant decisions. One of the main features of I4.0 is its adaptability to the human needs, this means that the items included in the I4.0 network are heterogeneous and they are large in number. The majority of I4.0 papers, which are focused on testing, describe a specific system or part of the I4.0 network. We have not found any paper that undertakes the testing of multiple connected IoT devices that will receive, process, and make decisions according to the complex and real data that travel through the network. In this article, we present IoT-TEG (Test Event Generator) 4.0, which is based on the test event generator system IoT-TEG. IoT-TEG 4.0 provides two new main contributions: the generation of test cases, which can include all the different types of data that the connected I4.0 devices under study can manage, and real-time testing. Additionally, its validation using real IoT programs is included and the results show that IoT-TEG 4.0 allows us to conduct tests that mimic real IoT system behaviors. [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]