frequency current
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2021 ◽  
Vol 63 (12) ◽  
pp. 1116-1123
Author(s):  
Tushar Sonar ◽  
Visvalingam Balasubramanian ◽  
Thiruvenkatam Venkateswaran ◽  
Dhenuvakonda Sivakumar ◽  
Sergey Konovalov

Abstract The gas tungsten constricted arc welding (GTCAW) process was used to join thin Su-718 alloy sheets to minimize alloying segregation and Laves phase precipitation in the fusion zone (FZ). The potentiodynamic corrosion behavior of GTCAW Su-718 alloy joints was studied and correlated to the microstructural features of welds. The potentiodynamic corrosion test was done in a 3.56 wt.-% NaCl solution to determine the corrosion rate of Su-718 alloy joints. The optical microscopy (OM) technique was used to analyze the microstructure of corroded weldments. The scanning electron microscopy (SEM) technique was used to study the Laves phase development in FZ. The SEM X-ray energy dispersive spectroscopy (EDS) technique was used to for elemental mapping of FZ. The corrosion resistance of Su-718 joints is inversely proportional to the precipitation of Laves phase in FZ. The GTCA welded Su-718 alloy joints disclosed superior corrosion resistance for the joints with lower Laves phase precipitation. It is correlated to the refining of FZ microstructure, which aids in minimizing the Laves phase precipitation. The joints with higher Laves phase precipitation revealed inferior corrosion resistance. It is attributed to coarsening of FZ microstructure, which raises the alloying segregation and leads to depletion of alloying elements in FZ. The dendritic core regions showed severe corrosion compared to the interdendritic regions. The corrosion resistance of GTCA welded Su-718 joints is better than that of CC-GTAW and PC-GTGAW joints and comparable to that of EBW and LBW joints. It refers to the arc constriction and high frequency current pulsation.


Vacuum ◽  
2021 ◽  
Vol 194 ◽  
pp. 110548
Author(s):  
Deshi Liang ◽  
Xingyu Guo ◽  
Jiyan Zou ◽  
Yongxing Wang ◽  
Zhihui Huang ◽  
...  

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Huijing Hu ◽  
Wai Leung Ambrose Lo ◽  
Xiaoyun Wang ◽  
Le Li ◽  
Ping Zhou

The objective of this study was to evaluate the interrater and intrarater reliability of electrical impedance myography (EIM) using handheld sensors of different sizes. Electrical impedance myography of the biceps brachii muscle of twenty healthy individuals was performed by two raters using both large and small sensors. The procedures were also repeated 5 to 8 days after the first recording session. The repeatability of the resistance, reactance, and phase angle at two different current frequencies (50 and 100 kHz) was assessed by the intraclass correlation coefficient (ICC). The ICCs of the large sensor were higher than those of the small sensor for both the intrarater and interrater reliabilities. High-frequency current tended to improve the ICC for the small sensor. These results indicate reasonable repeatability of the handheld electrode arrays for EIM measurements. The findings suggest that electrode array should be selected appropriately according to the size of the tested muscle.


2021 ◽  
Vol 2096 (1) ◽  
pp. 012001
Author(s):  
M Pustovetov

Abstract There is a problem of damage of bearings of traction induction motors of electric trains Lastochka by electric current. Based on the fact that the bearings have a ceramic insulation coating, and the cases of its electrical breakdown is not fixed, the authors put forward a version that a high-frequency current flows through the bearing as through an electric capacitance. The analysis show that the cause of the current can be a radio standard GSM-R. The proposed technical solution against the damage of bearings: the use of grounding shaft rings, replace the bearings on the other with ceramic rolling elements, arrangement of separate high-frequency grounding for the GSM-R antenna.


2021 ◽  
Vol 2103 (1) ◽  
pp. 012189
Author(s):  
A M Ivanov ◽  
A V Klochkov

Abstract Results are presented of a study of commercial blue and UV light-emitting diodes based on structures with InGaN/GaN quantum wells. An accelerated aging was provided by currents of 80 – 190 mA under a forward bias with duration not exceeding 3 h. The study demonstrated the possible rise in the external quantum efficiency by 20% relative to that in the starting samples. The possible physical mechanisms responsible for the rise in the quantum efficiency and for the formation of a low-frequency current noise are presented.


2021 ◽  
Vol 2061 (1) ◽  
pp. 012050
Author(s):  
A N Malyshev ◽  
A N Panarin ◽  
V V Debelov ◽  
M D Mizin

Abstract The article presents the theoretical foundations of the device and the principle of control of a power electric drive. An overview of the main structural elements and the requirements for the electric drive are made. Power electric drive control systems using inverter converters are considered: frequency-current control based on a current inverter; frequency-current control based on a voltage inverter; direct torque control; vector field control. The main provisions of the use of simulation and physical modeling in the development of an electric drive are presented. On the basis of the previous analysis, the best solutions allowing modeling the electric drive have been selected. The choice of the element base has been substantiated and the development of a physical model has been carried out.


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