A type of inverter power supply based on harmonic elimination PWM control

In order to output sine wave with small degree of distortion and improve stability,a type of inverter power supply is designed based on harmonic elimination pulse-width modulation(PWM)control.The rectifier and filter are added to input circuit of the inverter.Single-phrase full-bridge inverter performs the function of converting direct current into alternating current(DC/AC).In the control circuit,single chip micyoco(SCM)AT89C2051 is used for main control chip to accomplish the hardware design of the control system.A given value of output frequency of the inverter is input in the way of coding.According to the output frequency code which is read,SCM AT89C2051 defined harmonic elimination PWM control data which will be selected.Through internal timing control,the switches are switched under this provision of PWM control data.Then the driving signals of the switches in the inverter are output from I/O of SCM AT89C2051 to realize harmonic elimination PWM control.The results show that adding Newton homotopic algorithm of harmonic elimination PWM control to corresponding software of the control system can make the quality of output voltage of the inverter higher and it will have broad application prospects.

Long-lasting microbial larvicides for controlling insecticide resistant and outdoor transmitting vectors:a cost-effective supplement for malaria interventions

The issues of pyrethroid resistance and outdoor malaria parasite transmission have prompted the WHO to call for the development and adoption of viable alternative vector control methods.Larval source management is one of the core malaria vector interventions recommended by the Ministry of Health in many African countries,but it is rarely implemented due to concerns on its cost-effectiveness.New long-lasting microbial larvicide can be a promising cost-effective supplement to current vector control and elimination methods because microbial larvicide uses killing mechanisms different from pyrethroids and other chemical insecticides.It has been shown to be effective in reducing the overall vector abundance and thus both indoor and outdoor transmission.In our opinion,the long-lasting formulation can potentially reduce the cost of larvicide field application,and should be evaluated for its cost-effectiveness,resistance development,and impact on non-target organisms when integrating with other malaria vector control measures.In this opinion,we highlight that long-lasting microbial larvicide can be a potential cost-effective product that complements current front-line long-lasting insecticidal nets(LLINs)and indoor residual spraying(IRS)programs for malaria control and elimination.Microbial larviciding targets immature mosquitoes,reduces both indoor and outdoor transmission and is not affected by vector resistance to synthetic insecticides.This control method is a shift from the conventional LLINs and IRS programs that mainly target indoor-biting and resting adult mosquitoes.