At the beginning of August 2020,the Rio Grande Valley(RGV)of Texas experienced a rapid increase of coronavirus disease 2019(abbreviated as COVID-19)cases and deaths.This study aims to determine the optimal levels of e...At the beginning of August 2020,the Rio Grande Valley(RGV)of Texas experienced a rapid increase of coronavirus disease 2019(abbreviated as COVID-19)cases and deaths.This study aims to determine the optimal levels of effective social distancing and testing to slow the virus spread at the outset of the pandemic.We use an age-stratified eight compartment epidemiological model to depict COVID-19 transmission in the community and within households.With a simulated 120-day outbreak period data we obtain a post 180-days period optimal control strategy solution.Our results show that easing social distancing between adults by the end of the 180-day period requires very strict testing a month later and then daily testing rates of 5%followed by isolation of positive cases.Relaxing social distancing rates in adults from 50%to 25%requires both children and seniors to maintain social distancing rates of 50%for nearly the entire period while maintaining maximum testing rates of children and seniors for 150 of the 180 days considered in this model.Children have higher contact rates which leads to transmission based on our model,emphasizing the need for caution when considering school reopenings.展开更多
This paper presents a transimpedance amplifier （TIA） capacitance detection circuit aimed at detecting micro-capacitance, which is caused by ultrasonic stimulation applied to the capacitive micro-machined ultrasonic ...This paper presents a transimpedance amplifier （TIA） capacitance detection circuit aimed at detecting micro-capacitance, which is caused by ultrasonic stimulation applied to the capacitive micro-machined ultrasonic transducer （CMUT）. In the capacitance interface, a TIA is adopted to amplify the received signal with a center frequency of 400 kHz, and finally detect ultrasound pressure. The circuit has a strong anti-stray property and this paper also studies the calculation of compensation capacity in detail. To ensure high resolution, noise analysis is conducted. After optimization, the detected minimum ultrasound pressure is 2.1 Pa, which is two orders of magni- tude higher than the former. The test results showed that the circuit was sensitive to changes in ultrasound pressure and the distance between the CMUT and stumbling block, which also successfully demonstrates the functionality of the developed TIA of the analog-front-end receiver.展开更多
文摘At the beginning of August 2020,the Rio Grande Valley(RGV)of Texas experienced a rapid increase of coronavirus disease 2019(abbreviated as COVID-19)cases and deaths.This study aims to determine the optimal levels of effective social distancing and testing to slow the virus spread at the outset of the pandemic.We use an age-stratified eight compartment epidemiological model to depict COVID-19 transmission in the community and within households.With a simulated 120-day outbreak period data we obtain a post 180-days period optimal control strategy solution.Our results show that easing social distancing between adults by the end of the 180-day period requires very strict testing a month later and then daily testing rates of 5%followed by isolation of positive cases.Relaxing social distancing rates in adults from 50%to 25%requires both children and seniors to maintain social distancing rates of 50%for nearly the entire period while maintaining maximum testing rates of children and seniors for 150 of the 180 days considered in this model.Children have higher contact rates which leads to transmission based on our model,emphasizing the need for caution when considering school reopenings.
基金Project supported by the National Natural Science Foundation of China(No.61127008)the Subsidized Program of the National High Technology Research and Development Program of China(No.2011AA040404)
文摘This paper presents a transimpedance amplifier （TIA） capacitance detection circuit aimed at detecting micro-capacitance, which is caused by ultrasonic stimulation applied to the capacitive micro-machined ultrasonic transducer （CMUT）. In the capacitance interface, a TIA is adopted to amplify the received signal with a center frequency of 400 kHz, and finally detect ultrasound pressure. The circuit has a strong anti-stray property and this paper also studies the calculation of compensation capacity in detail. To ensure high resolution, noise analysis is conducted. After optimization, the detected minimum ultrasound pressure is 2.1 Pa, which is two orders of magni- tude higher than the former. The test results showed that the circuit was sensitive to changes in ultrasound pressure and the distance between the CMUT and stumbling block, which also successfully demonstrates the functionality of the developed TIA of the analog-front-end receiver.
