Sign in

*Physical evolution has its limits in the long term.

The fact that the Earth will not last forever poses a fiendish challenge to all the lives on the planet. No matter how successfully life forms have evolved in the Earth’s environment, they will inevitably go extinct once their home planet…


The news about the arrival of Covid-19 vaccines was exciting last year. Many people, however, are still hesitant to get immunized.

It is vaccinations that will end the pandemic at the lowest cost. I think that a vaccination dashboard is needed for the illustration of vaccine quality.

The dashboard includes…


We know the covid-19 virus mostly spreads through close contacts between people. While close contacts are greatly limited in public, they are generally accepted at home. It is time to introduce transmission control into homes when a lockdown is in place or when the number of cases is escalating. Measures…


Mathematics involves a lot of calculation with numbers. Since the calculating process is a logical one, it is important for a language to form the right words for numbers. Twenty-six, for instance, is a right word for 26, because ‘twenty-six’ indicates 2 before 6. Sixteen, on the other hand, is…


A creative problem-solver needs logical thinking with imagination, because imagination enables one to form something new in the mind while logical thinking helps to distinguish an effective solution from impractical ones.

Without imagination, you will probably get stuck in a new problem. Without logic, on the other hand, you are…


Most patients with Covid-19 can be infectious about two days before they develop symptoms. Some patients who never show any symptoms can still infect others before their recovery. The transmission during both asymptomatic periods is hard to detect.
As asymptomatic patients hardly cough or sneeze, their spread of the virus should…


As schools are usually empty at weekends, it is possible to reduce the density of students by keeping schools open on Saturday and Sunday. In theory, the density will be reduced by 28% (2/7=28%). For example, if a school has 5 classrooms and 5 classes, then divide students evenly into…


Since most of Covid-19 infection has spread from person to person indoors, smartphones should be able to find out indoor contacts when making a risk evaluation of infection for users. There are two methods to detect whether people are inside a building or not.

1. The GPS signals are usually…


Since Google and Apple made changes to Android and iPhone operating systems to facilitate digital contact tracing, many countries have been developing Bluetooth-based apps. …


A single figure doesn’t tell much. The relationship between two numbers is more interesting, especially between one and the total number of confirmed cases.

*The proportion of patients who have recovered: the higher, the better.

A high rate of recovery is usually due to a great proportion of the patients…

Xu Jun

A learner.

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store