Measuring complex for determining the characteristics of high-voltage silicon carbide Schottky diodes in impulse modes

This paper describes a developed automated research measuring complex that allows one to determine the parameters of currents, voltages and power of silicon carbide Schottky diodes when applied reverse voltage impulses with amplitudes from 400 to 1000 V. The research measuring complex was tested on DDSH411A91 («GRUPPA KREMNY EL») and C3D1P7060Q (Cree/Wolfspeed) silicon carbide Schottky diodes and allows to determine their maximum values of the rate of rise of reverse voltage dV/dt (877 V/ns and 683 V/ns). Also, the maximum values of the current rise rate dI/dt were determined for DDSH411A91 (3.24 A/ns) and C3D1P7060Q (3.72 A/ns) diodes. For the first time it was established that, when a reverse voltage impulse with an amplitude of 1000 V is applied, the maximum values of instantaneous fullpower reach 1419 VA for the DDSH411A91 diode and 1638 VA for the C3D1P7060Q diode.

A Discussion on Sea Level Rise, Rate Ad Acceleration. Venice as a Case Study

The paper discusses the equations used to represent the sea level rise, and in particular the second-order polynomial, generally preferred because its second-order coefficient is related to acceleration. The long series of the sea level rise in Venice offers a particularly useful case study from 1350 to 2016, because it may be equally represented, at the same level of explained variance, by an exponential or a quadratic best-fit equation. The first-order and the second-order derivatives respectively represent the rate and the acceleration of sea level rise. The derivatives obtained from the second-order polynomial representation generate a linear rate and a constant acceleration, while those derived from an exponential preserve the exponential character. The two rates (i.e. from the quadratic and the exponential equations), and the two accelerations are characterized by different equations and different plots, but their average values are the same. The second-order polynomial with constant acceleration is in line with a climate with constant forcing factors; the exponential with a dynamic condition with increasing forcing factors and acceleration. Mathematical formulae and physical consequences are discussed in the framework of different scenarios. Finally, the trend-forecast extrapolation is discussed and applied to the case study of Venice. It is shown that, in the most optimistic assumption of forcing increasing at unchanged rate, the sea level in Venice will rise by 33.8 ± 4 cm over this century, that may be compared to the 31 cm of the similar, most optimistic prediction made by IPCC for business-as-usual.

Experimental Study and Mathematical Modeling of the Processes Occurring in ZrN Coating/Silumin Substrate Systems under Pulsed Electron Beam Irradiation

This paper presents a study of a combined modification of silumin, which included deposition of a ZrN coating on a silumin substrate and subsequent treatment of the coating/substrate system with a submillisecond pulsed electron beam. The local temperature on the samples in the electron-beam-affected zone and the thickness of the melt zone were measured experimentally and calculated using a theoretical model. The Stefan problem was solved numerically for the fast heating of bare and ZrN-coated silumin under intense electron beam irradiation. Time variations of the temperature field, the position of the crystallization front, and the speed of the front movement have been calculated. It was found that when the coating thickness was increased from 0.5 to 2 μm, the surface temperature of the samples increased from 760 to 1070 °C, the rise rate of the surface temperature increased from 6 × 107 to 9 × 107 K/s, and the melt depth was no more than 57 μm. The speed of the melt front during the pulse was 3 × 105 µm/s. Good agreement was observed between the experimental and theoretical values of the temperature characteristics and melt zone thickness.

Research on the Thermal Characteristics of an 18650 Lithium-Ion Battery Based on an Electrochemical–Thermal Flow Coupling Model

Aiming at the complex experimental conditions of multi-physical field coupling in the analysis of thermal characteristics of lithium-ion batteries, a three-dimensional electrochemical-thermal flow coupling model for lithium-ion batteries was established using COMSOL Multiphysics software. Through the analysis of simulation results, the thermal characteristics of lithium-ion batteries for electric vehicles were explored from the aspects of heat generation and dissipation. It was found that increasing the charge–discharge rate and the electrode thickness will increase the temperature rise rate of lithium-ion batteries, and the temperature rise rate of lithium-ion batteries is the highest during their first time charging and discharging. Increasing the airflow velocity and reducing the size of the inlet flow area can improve the cooling effect on the cell. Under a single inlet, the cooling effect of the airflow field entering from the negative electrode is better than that from the positive electrode.

Study of Influential Factors on the Dielectric Strength of [UPE/BaTiO3] Nanocomposites

Unsaturated polyester resin (UPE) was used as a base material and barium titanite nanoparticles (BaTiO3) (50-7-nm) as a support material, with different weight ratios (0.25,0.75,1.25,2 wt%), to prepare a nanocomposite material. The research models were prepared according to the standard specifications and with different thicknesses (≈ 1.1,1.8,2.2,2.7 mm) to show the effect of thickness, number of cycles, percentage of addition and voltage rise rate at (5 kv/s and 0.5 kv/s) on the dielectric strength (Ebr) of the prepared material. The results showed that Ebr decreased with increasing the thickness of the material, BaTiO3 additive rate and the number of cycles. Dielectric strength (Ebr) increases with increasing of voltage rise rate.

SLR Estimation Using CEEMDAN Near the Korean Peninsula

The rise of sea levels due to global warming is a problem of concern at an international scope and the causes are already known relatively clearly. Every year, the Intergovernmental Panel on Climate Change (IPCC) creates a scenario for greenhouse gas emissions and predicts the global average sea-level rise rate accordingly. It is necessary to estimate the rate of sea-level rise to date in creating such a scenario. In particular, since the height of the sea level changes (SLC) continuously, the errors of SLC may occur due to various causes with a fragmental analysis. To estimate the sea-level rise accurately, we applied Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN) is based on the Empirical Mode Decomposition (EMD) to decompose the tidal level. Through this, we discover that the differences in the local sea-level rise rate occurred even within a small area. To understand each component of tide level decomposed through CEEMDAN, we confirm the component-wise/regional correlation between tidal stations. In addition, we looked at how local sea-level rise correlated with the global meteorological phenomenon, El Niño-Southern Oscillation (ENSO) which is one of the most influential recurring climate patterns Socioeconomically.

Projection of future sea level rise in the East Asian Seas based on Global Ocean-Sea Ice Coupled Model with SRES A1B Scenario

To project the future sea level rise in the East Asian Seas due to global warming, regional sea level variations are downscaled from three climate system models (GFDL-CM2.1, ECHAM5/MPI-OM, MIROC3.2(hires)) using a global ocean-sea ice coupled model with non-Boussinesq approximation. Based on the SRES A1B Scenario, the projected ensemble mean sea level rise (rate of rise) for the East Sea, Yellow Sea and East China Sea from 1995 to 2050 is 15.60cm (2.84mm/year), 16.49cm (3.0mm/year) and 16.43cm (2.99mm/year), respectively. With the inclusion of the future change of land ice melting and land water storage, the mean sea level rise (rate of rise) increases to 33.55cm (6.10mm/year) for the East Sea, and 34.38~34.44cm (6.25~6.26mm/year) for the Yellow and East China Seas. The present non-Boussinesq ocean model experiment shows that the future sea level rise in the East Sea is mainly due to the steric component changes by heat content increase. On the other hand, the future sea level rise in the Yellow and East China Seas appears to be mainly associated with the non-steric component change by water mass convergence.

Investigation on the method of battery self-heating using motor pulse current

The charging and discharging performance of lithium-ion battery at low temperature will decline greatly, which seriously affects the adaptability of electric vehicles at low temperature. This paper proposes to use the inductance characteristic of the motor stator and the switching control characteristic of the motor controller to form pulse current in the battery, and realize the self-heating of the power battery at low temperature. Using this method the heating of the battery can be achieved without any additional hardware or cost. The experimental result shows the average temperature rise rate of the power battery reaches 2.88°C/min. And the influence of different parameters on the heating effect is analyzed through the experiments, including IGBT switching frequency, d-axis voltage, motor-rotor position, and battery internal resistance.

Experimental Study on the Fire Resistance Performance of Partition Board under the Condition of Small Fire Source

Fire safety of ancient wooden buildings is one of the most important issues in the world. In this paper, partition boards with different thicknesses from 15 to 25 mm were heated by a 15-cm-diameter pool fire and a methane Bunsen burner. The temperatures and the carbonization rate of partition boards were measured and analyzed. The results show that when a pool fire was used to heat the wood sample at a distance of 30 cm, two flames appear on the sample surface. When a Bunsen burner heats the sample, the sample is burned until the center point is burned through. The thickness of the sample is increased by 5 mm, and the acceleration time of the temperature rise rate at the center is doubled. Under the condition of a pool fire, the thickness of the sample is increased by 5 mm, and the average carbonization rate at the center point is reduced by 40%. Under the condition of Bunsen burner, the average carbonization rate of the center point decreases exponentially when the thickness of the sample increases by 5 mm. In the case of the same fire source, the carbonization rate of the samples with different thicknesses has the same change trend in the horizontal and vertical directions. Compared with the pool fire, the burn-through time of the center point of the sample is reduced in the case of the Bunsen burner for a sample of the same thickness, and the average carbonization rate of each measuring point increases.

The Hazards Analysis of Nickel-Rich Lithium-Ion Battery Thermal Runaway under Different States of Charge

The lithium-ion battery industry has been developing rapidly, with energy density and capacity constantly improving. However, the ensuing safety accidents of lithium-ion power batteries have seriously threatened the personal safety of passengers. Therefore, more and more attention has been paid to the thermal safety research of lithium-ion batteries, such as thermal runaway (TR) mechanism analysis and prevention methods, etc. In this paper, the nickel-rich 18650 lithium-ion batteries with Li[Ni0.8Co0.1Mn0.1]O2 cathode in different states of charge (SOC) are taken to investigate the TR characteristics using an extended volume plus acceleration calorimeter (EV+-ARC). In order to evaluate the TR characteristics, some characteristic parameters such as battery voltage, surface temperature, temperature rise rate, etc. are selected from the experiment to analyze the influence of SOC on the critical state of TR. It can be seen from the experiment results that the maximum temperature of the battery surface decreases with the decrease of SOC, while the self-generated heat temperature and TR trigger temperature increases with the decrease of SOC.