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Nowadays, pyramid schemes have caused extremely negative effects on people’s lives and seriously damaged the social economy. With the rapid development of network and communication technology, people’s direct or indirect social interaction is more frequent, which makes the phenomenon of pyramid schemes more serious. Therefore, it is necessary to study transmission mechanisms and transmission rules of pyramid schemes. In order to study the influence of government management and social interaction topology on the spreading of pyramid schemes, a novel SHIPR (susceptible-hesitator-involved-punished-resister) pyramid scheme spreading model is proposed on scale-free networks. The spreading dynamics of pyramid schemes are analyzed in detail by mean-field theory. Then, the basic reproduction number $R_{0}$ and equilibria are got. Theoretical analysis shows that the basic reproduction number $R_{0}$ has a great correlation with government crackdown intensity for involved individuals, the coverage rate of government anti-pyramid scheme publicity for susceptible individuals and hesitator, and social interaction topology. Furthermore, the local asymptotic stability of fraud-elimination equilibrium is analyzed based on the Routh-Hurwitz criterion, the global asymptotic stability of the fraud-elimination equilibrium is discussed by the Lyapunov function, the global attractivity of fraud-prevailing equilibrium is proved in detail by comparison principle. Finally, numerical simulations verify the theoretical analysis results.

The alternate control systems have been elaborated in detail and have been applied in many areas, such as smart home, smart transportation, etc. However, although alternate control systems with input delays widely exist in real life, not so much attention has been given to them. This paper mainly studies the stability of alternate control systems with input delays. A new mathematical model of the alternate control system with time delay input is proposed. By using a Lyapunov function and linear matrix inequalities, the exponential stability conditions is given. At last, the effectiveness and feasibility of the method are verified through experimental simulations.

Research the transmission efficiency optimization problem of magnetic coupling resonant wireless charging system. According to the transmission principle of resonant wireless charging, the system multi-parameter matching problem is optimized to make the wireless charging system work in the best state. Construct an equivalent model of series-series compensation topology, and obtain three key parameters that affect the transmission efficiency of the system: frequency, distance and load resistance. Using the particle swarm optimization algorithm with compression factor, the best of the three key parameters is obtained. The matching value, compared with the system that only optimizes two key parameters, proves that this method can find the best matching value between the parameters faster and more accurately within the set feasible range, and the system transmission efficiency reaches Optimal. The effectiveness of the algorithm and the correctness of the analysis process are verified by a Matlab simulation example.

This paper presents an anti-overcharged high-dV/dt-immunity capacitive level shifter with dynamic discharge control (DDC) for half-bridge GaN driver. The DDC prevents overcharge of the floating power supply capacitor during high negative dV/dt transitions and is suitable for a wide variation range of negative dV/dt transitions of floating power supply. Moreover, a fault-logic blanking block is introduced to guarantee the robust of output logic during ultra-high dV/dt transitions. The proposed Level shifter is fabricated in a 0.18µm BCD process and occupies an active chip area of 0.034mm2. Simulation results demonstrate that the propagation delay is less than 0.8ns at 50V level shifting and keeps almost constant when the floating ground ranges from -3V to 50V. The positive dV/dt immunity is 300V/ns. The negative dV/dt is 170V/ns under the condition that the level shifting capacitor does not discharge to floating power supply.

In order to study the influence of the number of centrifugal impeller blades on the aerodynamic performance of the centrifugal compressor, the influence of the number of blades with and without splitter on the pressure ratio, isentropic efficiency, mass flow, shaft power and outlet airflow angle of the compressor is analysed. The research results show that for transonic miniature centrifugal compressors, increasing the number of blades can improve the compressor’s isentropic efficiency and pressure ratio. The compressor’s pressure ratio and isentropic efficiency first increase and then decrease with the increase in the number of blades. When the number of blades with splitter blades is 12, the pressure ratio of the centrifugal compressor reaches the maximum of 1.69, and the isentropic efficiency is 68.8%; increasing the splitter blade compressor has little change in pressure ratio, but can improve the compressor Isentropic efficiency and mass flow. The number of blades is an effective method to improve its isentropic efficiency and pressure ratio. This analysis method provides a reference for the judicious selection of the number of blades and provides a reference for the design of miniature centrifugal compressors under high Reynolds number.

A programmable slew rate (SR) control by dynamically modulating power supply of GaN HEMT gate drive is proposed in this paper to optimize EMI and efficiency for power converters. This single-channel gate driver has been fabricated in a $0.35 \mu \mathrm{m}$ HV CMOS process, where the active area is $1160\times 1032 \mu \mathrm{m}^{2}$ and V DD regulator ($\approx 937 \times 382 \mu \mathrm{m}^{2}$) has also been implemented to ensure a wide power supply range (6-18V). The proposed high-speed circuit can work up to 2MHz with transmission delay of 11ns and a small gate-drive voltage droop (

The characteristics of GaN devices meet the design requirements of high-frequency and high-power density in next-generation power electronics technology well. However, the superior performance of GaN devices depends heavily on the high-reliability gate drivers. This paper reviews the key issues in the GaN gate driver, such as the design of high-speed level shifter, the design of floating power rail, EMI optimization, dead time optimization and other issues. Moreover, the feasible solutions and latest research progress on various issues are presented.

In order to study the dynamics of social media marketing, we propose a novel dynamics model of social media marketing on scale-free networks. We divided the whole population into four groups: potential, hesitant, satisfied and unsatisfied (PHSU) consumers. Using the mean-field and spectral radius theory, we derive the threshold which can forecast the marketing dynamics, and the equilibrium states of our model are also proved. Numerical simulations are presented to verify and extend theoretical results. Furthermore, we give and compare some marketing strategies in simulations.

Fairness in task allocation is important among agents in multi-agent cooperation, which is not taken into consideration in existing works. This paper studied the cooperative hunting problem with the fairness consideration in a multi-agent system consisting of n predators and one prey. According to the practice requirement, the hunting problem is transformed into making agents a circular formation around the moving prey. A novel cooperative hunting control scheme was presented, consisting of two parts: fair distribution based on the fairness and specified-time set point tracking. Using the proposed method, the multi-agent system can simultaneously reach the target at a specified-time to achieve the hunting, and their driving distances (fairness index) are as equal as possible. Simulations are provided to verify the effectiveness of the cooperative hunting scheme.

The gate reliability of normally off p-GaN gate AlGaN/GaN HEMTs and its underlying physical mechanism were investigated in a long-term recovery period after long-term forward gate stress. For the first time, a nondestructive gate degradation featuring a first degradation and then followed by a self-recovery dynamic was observed after a rigorous long-term (13–53 ks) forward gate stress. To elucidate the gate degradation kinetics, the static gate current, transfer characteristic and transient gate current were characterized before and after the gate stress as well as in the recovery intervals. During the stress, hole-injection together with trap-generation and hole-trapping concurred in AlGaN barrier is observed. Subsequently, electrons attracted by the trapped holes are persistently trapped in the AlGaN barrier, which leads to an electron energy barrier lowering and a continuing gate current increase in the recovery intervals. The hole-injection, hole-trapping, electron-trapping and hole/electron-detrapping take place in sequence during the stress and recovery process are reinforced by the inhomogeneous shift in VTH. The observed unique gate degradation dynamics and its underlying mechanism are of great value for p-GaN gate optimization to achieve improved gate reliability.

The advanced floating bias control techniques (FBCT) for GaN devices are proposed in this paper, which aims at solving negative voltage transient issues present at switching node of power stage during dead time. It adopts maximum power-supply tracking to reduce time delay of level shifter and active clamping for bootstrap voltage to avoid overvoltage conditions. This high-reliability half-bridge GaN gate driver has been fabricated in a $0.5\boldsymbol{\mu} \mathbf{m}$ 80V HV CMOS process and occupies a chip area of $1699\times 1522\boldsymbol{\mu} \mathbf{m}^{2}$ where the active area of FBCT with internal bootstrap diode is $1350\times 620\boldsymbol{\mu}\mathbf{m}^{2}$ . The response time of level shifter is only 1.97ns in the process of turning on high-side power switch. Transmission delay is small and there are no logic errors or latch-up issues in the gate driver due to the negative voltage transient. Bootstrap voltage ripple based on active clamping technique is well controlled over a wide frequency range (166mV@500kHz∼ 797mV@5MHz at $\boldsymbol{C}_{\mathbf{boot}}=0.1\boldsymbol{\mu}\mathbf{F}$ ). The total quiescent current consumed by FBCT is only $90\boldsymbol{\mu} \mathbf{A}$ .

A high-voltage half-bridge gate drive circuit for E-mode GaN device with high-speed low-power and high-noise-immunity level shifter is proposed in this paper. It adopts digital-level detection concept by combining fast-slewing and output-maintain circuits in high noise environments to achieve both small response time and high dV sw/dt noise immunity. The proposed gate driver is fabricated in 0.5μm 80V HV CMOS process where the active area is 1699×1522μm2. Simulation and experimental results of the level shifter demonstrate that propagation delay is only about 1.618ns and dV sw/dt noise immunity is up to 50V/ns with a low FOM equal to 0.04ns/μm·V.

This paper presents a fully-integrated and fast-transient capacitor-less low-dropout regulator (LDO) with high loop gain and bandwidth in full load range for SoC application. It utilizes a combination of a signal- and transient-current boosting (STCB) error amplifier (EA) with transient enhancement circuit (TEC) and a push-pull differentiator to drive gate capacitance of the power transistor. The STCB-based EA with TEC ensures fast response of the regulator and the differentiator is also adopted to enhance the loop stability while improving transient response simultaneously. Moreover, adaptive biasing is implemented in the circuit to compensate decrease of loop gain and bandwidth at heavy load. The proposed LDO is fabricated in a 0.5μm CMOS process and occupies an active chip area of 0.077mm2. Simulation results demonstrate that it can deliver 100mA load current at 100mV dropout voltage. The voltage spike at the output, undergoing a maximum load current change, is controlled below 300mV and good line/load regulation is achieved at the same time.

A low-dropout regulator (LDO) with a wide-bandwidth feedforward supply noise rejection technique to maximize power supply rejection (PSR) at middle-to-high frequency is presented in this paper. The concept is based on a bandpass filter design without using a large voltage-gain amplifier in the feedforward path. For the PSR filter design, the total on-chip capacitance is about 36pF by utilizing an nwell gate capacitor with high capacity in the process. This circuit has been analyzed and verified in a 0.5μm CMOS process. From the experimental results, the proposed LDO can operate with a dropout voltage of 150mV at maximum load of 25mA. The quiescent current is only 19μA at light load. It achieves a PSR better than −45dB up to 10MHz with a 4μF output capacitor.

Variable on Time (VOT) control is proposed in the paper. Compared to conventional constant on time (COT) control, the on time of VOT control is modulated by output of error amplifier, rather than fixed voltage. VOT controlled buck converter shows significant duty cycle extension than COT control, especially for high switching frequency and wide input/output range applications, such as DVS converters. The duty cycle limitation of COT control is then broken through. The small signal model derivation based on Describing Function (DF) is given. A 1MHz 12V-1.2V buck converter with VOT control is designed with 0.35μm BCD process. Simulation results show that the recovery time is 5μs for 4A load step, and the undershoot voltage is decreased from 50mV to 35mV, by using VOT control. The voltage scaling speed is 20μs/V for 47μF output capacitor. The reference up-tracking shows FOM of 0.42s/(F·V), which is much better than previous works.