Detection of ULF electromagnetic emissions as a precursor to two earthquakes in China

The geomagnetic data recorded by Kashi and Jinghai observatories in China were analyzed with improved polarization method. We compared the result around 0.01 Hz which is thought to be useful to detect the ULF anomaly with the result around 0.1 Hz which was inferred from the earthquake depth according to the skin effect, and found that 0.1 Hz is more proper to detect the ULF anomaly for both earthquakes studied in this paper.

Statistical study on great geomagnetic storms during solar cycle 23

Characteristics of great geomagnetic storms during solar cycle 23 were statistically investigated. Firstly, we focused on the uniqueness of solar cycle 23 by analyzing both the great storm number and sunspot number from 1957 to 2008. It was found that the relationship between the sunspot number and great storm number weakened as the activity of the storms strengthened. There was no obvious relationship between the annual sunspot number and great storm number with Dst≤-300 nT. Secondly, we studied the relationship between the peak Dst and peak Bz in detail. It was found that the condition Bz〈-10 nT is not necessary for storms with Dst≤-100 nT, but seems necessary for storms with Dst≤-150 nT. The duration for Bz≤-10 nT has no direct relationship with the giant storm. The correlation coefficient between the Dst peak and Bz peak for the 89 storms studied is 0.81. After removing the effect of solar wind dynamic pressure on the Dst peak, we obtained a better correlation coefficient of 0.86. We also found the difference between the Dst peak and the corrected Dst peak was proportional to the Dst peak.

The incubation period of COVID-19: a global meta-analysis of 53 studies and a Chinese observation study of 11 545 patients

Background:The incubation period is a crucial index of epidemiology in understanding the spread of the emerging Coronavirus disease 2019(COVID-19).In this study,we aimed to describe the incubation period of COVID-19 globally and in the mainland of China.Methods:The searched studies were published from December 1,2019 to May 26,2021 in CNKI,Wanfang,PubMed,and Embase databases.A random-efect model was used to pool the mean incubation period.Meta-regression was used to explore the sources of heterogeneity.Meanwhile,we collected 11545 patients in the mainland of China outside Hubei from January 19,2020 to September 21,2020.The incubation period ftted with the Log-normal model by the coarseDataTools package.Results:A total of 3235 articles were searched,53 of which were included in the meta-analysis.The pooled mean incubation period of COVID-19 was 6.0 days(95%confdence interval[CI]5.6–6.5)globally,6.5 days(95%CI 6.1–6.9)in the mainland of China,and 4.6 days(95%CI 4.1–5.1)outside the mainland of China(P=0.006).The incubation period varied with age(P=0.005).Meanwhile,in 11545 patients,the mean incubation period was 7.1 days(95%CI 7.0–7.2),which was similar to the fnding in our meta-analysis.Conclusions:For COVID-19,the mean incubation period was 6.0 days globally but near 7.0 days in the mainland of China,which will help identify the time of infection and make disease control decisions.Furthermore,attention should also be paid to the region-or age-specifc incubation period.

Research on the Loss Sharing Contract in Supply Chain Under Asymmetric Information

In this study, the coordination contract of internal and external losses of supply chain under asymmetric information is studied. Firstly, the profit functions of supplier and manufacturer are established respectively. Secondly, the contract under unilateral and bilateral moral hazard is designed.Finally, a numerical example is given to analyze the coordination contract. It is proved that the overall coordination of supply chain can be achieved through loss sharing contract, and the quality level and overall profit can be improved.