Влияние редкоземельных металлов на стеклообразующую способность и кристаллизацию аморфных сплавов CoFeSiBNb

In present work amorphous alloys Co48Fe25Si4B19Nb4-R (R = Nd, Sm, Tb, Yb) were obtained by planar flow casting in the form of ribbons with 3-5 mm wide and 35-45 μm thickness. It was found that crystallization process goes into two stages and depends on the used rare-earth addition and its content in the alloy by differential thermal analysis method. Glass-forming ability criteria were calculated. It is shown that paramagnetic Curie temperature of alloys in liquid state can be used as their a-priori criterion of glass-forming ability.

PMMA Application in Piezo Actuation Jet for Dissipating Heat of Electronic Devices

The present study utilizes an acrylic (PMMA) plate with circular piezoelectric ceramics (PC) as an actuator to design and investigate five different types of piezo actuation jets (PAJs) with operating conditions. The results show that the heat transfer coefficient of a device of PAJ is 200% greater than that of a traditional rotary fan when PAJ is placed at the proper distance of 10 to 20 mm from the heat source, avoiding the suck back of surrounding fluids. The cooling effect of these five PAJs was calculated by employing the thermal analysis method and the convection thermal resistance of the optimal PAJ can be reduced by about 36%, while the voltage frequency, wind speed, and noise were all positively correlated. When the supplied piezoelectric frequency is 300 Hz, the decibel level of the noise is similar to that of a commercial rotary fan. The piezoelectric sheets had one of two diameters of 31 mm or 41 mm depending on the size of the tested PAJs. The power consumption of a single PAJ was less than 10% of that of a rotary fan. Among the five types of PAJ, the optimal one has the characteristics that the diameter of the piezoelectric sheet is 41 mm, the piezoelectric spacing is 2 mm, and the length of the opening is 4 mm. Furthermore, the optimal operating conditions are a voltage frequency of 300 Hz and a placement distance of 20 mm in the present study.

Thermal analysis method of electromagnetic linear actuator based on multiphysics coupling model

Electromagnetic linear actuators (ELAs) may be confronted with unsatisfactory performance when subjected to overheating. Therefore, it is significant to clarify its thermal characteristics and design the thermal performance requirements. A thermal analysis method based on multiphysics coupling model was presented, which uses the non-simplified loss distribution as the heat source to calculate the temperature field, adjusts the material properties by temperature, and considers the interaction between motion (including impact) and loss. More importantly, an improved universal equivalent winding to satisfy the condition of real compact concentrated winding was developed. Finally, the validity of this approach was verified through the experiment, and the regularity of temperature was summarized. The results show that the error of simulation and experiment is less than 6% and the permissible continuous operation frequency is no more than 30 Hz. The approach proposed in this paper can be employed not only to the ELA, but also to the design and analysis a wide range of electromagnetic machines.

Doping Dependent Electro-Thermal Analysis of 4H-SiC Power MOSFET

This paper presents a comparison of device behaviors of 4H-SiC DMOSFET (DMOS), trench MOS-FETs without (T-MOS) and with a p-shield (TP-MOS). The influence of doping density on device temperature distribution is investigated using the electro-thermal analysis method. It is established that the formation of a hot-spot (the highest temperature) is formed at the junction between the p-base and the n-drift region next to the corner of the trench gate. This hot spot temperature increases with rising doping density of the n-drift region. Additionally on-resistance (Ron) of the three examined structures increase when temperatures rise from 300 K to 523 K. At 300 K, the on-resistance of the TP-MOS was 2.7 mil cm2 32.5% lower than that of T-MOS while 67.47% lower than that of DMOS. When the temperature rises to 523 K, TP-MOS structure, with an on-resistance of 5.26 mil cm2 is obtained, which is lower by 34.25% and 73.7% with comparison to those of T-MOS and DMOS, respectively.