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I remember experiencing many rainy weekends and Mondays. To see whether this is a fact, I downloaded #weather data from #GHCND:USW00053152 from 2022-09-01 to 2024-05-01 and summed up the precipitations for each weekday.
It turns out that the total #precipitation for each weekday is (from Sunday to Saturday, in unit of mm): 239.0, 250.9, 212.9, 156.6, 172.0, 160.3, 219.8. Surprisingly we do have especially less #rain for Wed, Thur, and Fri.
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手纸本
何为手纸本?
- Categories: literature
- Tags: from zhihu, literary composition, short story, chinese
Introducing bra–ket notation to math learners
Bra–ket notation is a good-looking notation! I am sad that it is not generally taught in math courses. Let me introduce it to you.
- Categories: math
- Tags: from zhihu, quantum mechanics
Even solutions to bound states in an odd number of potential wells
We try solving the even function solutions to the time-independent Schrödinger equation for the potential such that (bound states).
- Categories: physics
- Tags: from zhihu, quantum mechanics
Defend our earth against aliens’ bullets!
The aliens intiated their attack to the earth! They shoot bullets with mass and speed from a far-awar planet. To defend, humans built a field that can repel the bullets. What regions are safe? The answer turns out to be the interior of a circular paraboloid.
- Categories: physics
- Tags: calculus, classical mechanics, kepler problem, from zhihu
This is what will happen after you get a haircut
Denote the length distribution of one’s hair to be , where is hair length, and is time. Considering that each hair may be lost naturally from time to time (there is a probability of for each hair to be lost within time range from to ) and then restart growing from zero length, how will the length distribution of hair evolve with time? It turns out that we may model it with a first-order PDE.
- Categories: math
- Tags: calculus, probability, pde
I want to invent a better way to read numbers
Reading numbers in English is a pain. I want to invent a better way to read numbers!
- Categories: language
- Tags: imagination
The longest all- substring of a random bit string
Given your probability of breaking the combo at each note, what is the probability distribution of your max combo in the rhythm game chart? I considered the problem seriously!
- Categories: math
- Tags: long paper, rhythm game, algorithm, probability
I made this, for the number of days in a week is prime
The number of days in a week is prime, so we cannot utilize weekly periods to help us remember periodical events unless the period is a multiple of 7. However, there may be something that we need to get reminded of which happens once per two days or three days. For example, I wash my hair once per two days and wash my clothes once per eight days. To solve the problem, I wrote a Ruby program to help remind me of those routines.
- Categories: programming
- Tags: selfhosting, linux, ruby
Using ntfy to warn me when my computer is discharging
I use udev and systemd to send a notification to my phone via ntfy automatically whenever my laptop is discharging.
- Categories: programming
- Tags: selfhosting, linux
How to construct mechanics in higher dimensions?
We can derive the equation of motion for mechanical systems in a Galileo universe with time dimensions and space dimensions by generalizing the principle of relativity and Hamilton’s principle.
- Categories: physics
- Tags: from zhihu, classical mechanics, imagination
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