Optimization of winding resistance for litz wire inductors is essential to reduce losses and improve energy transfer efficiency in electrical power systems. In this study, an approximate model for the optimization of winding resistance in litz wire inductors based on Dowell's equation is developed in three frequency ranges. The proximity and skin effects are analysed separately and subsequently combined to obtain an approximation with minimum theoretical error. Two error functions are defined to determine the frequency ranges for which the approximation is valid. Based on this Dowell's model approximation, it is found that, with the other parameters of the inductors fixed, both the porosity factor and conductivity have an optimal value that minimizes AC resistance for the litz wire windings. Thus, expressions for the optimum porosity factor and conductivity are derived, the optimization schemes under different practical engineering conditions are also given. The theoretical results are in good agreement with the experimental measurements, which indicates that the proposed model is valid for three frequency ranges, and the proposed optimization method is practical and suitable.

This paper proposes a new reader solenoid coil with a metal tube for use in high-temperature water, mud, and other impurities in an oil well downhole. The coil can read commands transmitted from the ground surface via inactive microtags and write the sensor data collected in the downhole into the microtags for transmission to the ground. By combining transformer theory and electromagnetic field theory, the main parameters of the reader solenoid coil in the harsh industrial environment in a downhole are calculated and the main factors responsible for RFID communication failure at 125±10 kHz of the reader solenoid coil are analyzed. Then, a mathematical model is developed to describe the relationship among the electromagnetic field density, the ac resistance of complex permittivity, and the complex permeability with water and the metal tube of the reader solenoid coil. Methods to reduce the changes in the inductance and resistance are presented. The minimum flux density of the reader solenoid coil is designed to provide a continuous energy supply to inactive microtags, and the identification rate by the reader is 100% at 125±10 kHz. Furthermore, the reader solenoid coil was tested in an industrial environment in the downholes of six oil well drilling systems for two years.

This study investigated the effective length of the reader solenoid coil used for oil-well drilling, and the time required for the communication between rapidly moving microtags and the reader solenoid coil attached to the equipment pipeline was calculated. The effective length of the solenoid coil was computed for both static and moving microtags. Then, a mathematical model was developed to describe the relationship among the effective length of the reader solenoid coil, baud rate, number of data bits, and microtag speed. Calculations were performed to design two reader solenoid coils, which were tested experimentally with a carrier frequency of 125 ± 10 kHz. The results show that the effective length of the reader solenoid coil is proportional to the microtag speed and number of data bits but inversely proportional to the baud rate. The proposed system provides a continuous energy supply to the microtags, and the moving microtag identification rate by the reader is 100%. The experimental and calculation results were in good agreement. Furthermore, reader solenoid coils of two lengths were used in the downholes of six oil-well drilling systems over two years.

Random testing is used extensively in functional verification of hardware systems. In practice, testing stops when a certain coverage criterion is achieved. However, testing has the inherent problem of being only able to expose bugs, not prove their absence. Thus, proving whether a potential bug exists or not under current verification efforts would be helpful to measure the completeness of testing. This paper proposes a probabilistic coverage analysis method to quantify the probability of bug existence for sequential circuit verification under random testing. The proposed method consists of an effective formula for computing the probability of a bug (assuming it exists) being detected in a sequential circuit. The formula is time complexity cubic to the number of coverage bins and linear to the number of test cycles. To validate the proposed method, it was implemented in MATLAB to calculate the probability of a bug being detected. Experimental results on 20,116 random instances indicate that, using Monte Carlo simulation, the proposed analysis method has an average absolute relative error of approximately 0.027%, comparing to 7.38% in existing work.

With the rapid development of the Internet of Things (IoT), improving the lifetime of nodes and networks has become increasingly important. Most existing medium access control protocols are based on scheduling the standby and active periods of nodes and do not consider the alarm state. This paper proposes a Q-learning and efficient low-quantity charge (QL-ELQC) method for the smoke alarm unit of a power system to reduce the average current and to improve the lifetime of the wireless sensor network (WSN) nodes. Quantity charge models were set up, and the QL-ELQC method is based on the duty cycle of the standby and active times for the nodes and considers the relationship between the sensor data condition and the RF module that can be activated and deactivated only at a certain time. The QL-ELQC method effectively overcomes the continuous state–action space limitation of Q-learning using the state classification method. The simulation results reveal that the proposed scheme significantly improves the latency and energy efficiency compared with the existing QL-Load scheme. Moreover, the experimental results are consistent with the theoretical results. The proposed QL-ELQC approach can be applied in various scenarios where batteries cannot be replaced or recharged under harsh environmental conditions.