天空вℓσи∂ @skyblond@qoto.org

给象友们一人一颗鹅卵石

Here it is: The first clear image of an eclipse of the Sun by the Earth, taken from the surface of the Moon.

This is what last night's lunar eclipse looked like from the Blue Ghost lander's perspective on the Moon. Amazing!

https://www.flickr.com/photos/fireflyspace/54386246629/in/dateposted/ #space #science #art #tech

3月11日河工大博士生杀导师案件，墙内已全网封锁消息。有传闻说，目击证人听到博士生一边用刀捅导师脖子，一边喊：还我数据！还我数据！也有传闻说，导师抢走博士生成果，给导师儿子发论文……种种传闻都符合我对国内学术圈（juan4）的了解。

最近十年，国内学术圈（juan4）环境严重恶化。各式各样的论文大跃进、项目课题大跃进、实验室大跃进、“双一流”大跃进……企图营造 “我国科技遥遥领先” 的大国幻象。

除了青年教师有论文和课题数量kpi，副高职称、正高职称有更高的论文和课题数量kpi。后者遂利用权力，剥削学生，让学生生产论文，第一作者署导师的名字。众所周知，即便作者名单里有你，但你若不是第一作者，招聘、考核、评职称的时候，根本不承认那是你的科研成果。

至于明抢学生论文、实验数据、田调资料的导师，数不胜数。我的一个同学，多年毕不了业，就是因为，他的博士论文的大部分，被他导师直接据为己有，成为导师评长江学者的垫脚石。而他连第二三四五作者都算不上，名字出现在致谢名单里。

这些靠偷、靠抢、靠抄袭的粗劣论文，占满了国内有限的学术刊物的版面，使博士生和青年教师发表论文难上加难，不得不花费六位数的巨额贿款，贿赂中介、贿赂期刊编辑，排队等待遥遥无期的发表……

甚至有宋尔卫之流，只手遮天，直接要了博士生们的命，还拆掉实验室，毁灭证据。

在这样的环境之下，博士生杀导师的案子，恐怕会越来越多。

什么鸡掰，“在法国这么多人共用一个断头台不会被感染吗？”
弹幕：活着才有发炎权
太烂了我哈哈大笑

@xyfdi

Atleast he fought back, unlike the USA, Putin owns our ass without firing a shot. Trump truely is a pathetic weak little man.

@dick

How NOT to pirate adobe products.....
mommyshandsomeboi
https://www.youtube.com/watch?v=TM6q1F45boQ

Why are QR Codes with capital letters smaller than QR codes with lower-case letters?

https://shkspr.mobi/blog/2025/02/why-are-qr-codes-with-capital-letters-smaller-than-qr-codes-with-lower-case-letters/

Take a look at these two QR codes. Scan them if you like, I promise there's nothing dodgy in them.

Left is upper-case HTTPS://EDENT.TEL/ and right is lower-case https://edent.tel/

You can clearly see that the one on the left is a "smaller" QR as it has fewer bits of data in it. Both go to the same URl, the only difference is the casing.

What's going on?

Your first thought might be that there's a different level of error-correction. QR codes can have increasing levels of redundancy in order to make sure they can be scanned when damaged. But, in this case, they both have Low error correction.

The smaller code is "Type 1" - it is 21px * 21px. The larger is "Type 2" with 25px * 25px.

The official specification describes the versions in more details. The smaller code should be able to hold 25 alphanumeric character. But https://edent.tel/ is only 18 characters long. So why is it bumped into a larger code?

Using a decoder like ZXING it is possible to see the raw bytes of each code.

UPPER

20 93 1a a6 54 63 dd 28  
35 1b 50 e9 3b dc 00 ec
11 ec 11

lower:

41 26 87 47 47 07 33 a2  
f2 f6 56 46 56 e7 42 e7
46 56 c2 f0 ec 11 ec 11  
ec 11 ec 11 ec 11 ec 11
ec 11

You might have noticed that they both end with the same sequence: ec 11 Those are "padding bytes" because the data needs to completely fill the QR code. But - hang on! - not only does the UPPER one safely contain the text, it also has some spare padding?

The answer lies in the first couple of bytes.

Once the raw bytes have been read, a QR scanner needs to know exactly what sort of code it is dealing with. The first four bits tell it the mode. Let's convert the hex to binary and then split after the first four bits:

The UPPER code is 0010 which indicates it is Alphanumeric - the standard says the next 9 bits show the length of data.

The lower code is 0100 which indicates it is Byte mode - the standard says the next 8 bits show the length of data.

Look at that! They both have a length of 10010 which, converted to binary, is 18 - the exact length of the text.

Alphanumeric users 11 bits for every two characters, Byte mode uses (you guessed it!) 8 bits per single character.

But why is the lower-case code pushed into Byte mode? Isn't it using letters and number?

Well, yes. But in order to store data efficiently, Alphanumeric mode only has a limited subset of characters available. Upper-case letters, and a handful of punctuation symbols: space $ % * + - . / :

Luckily, that's enough for a protocol, domain, and path. Sadly, no GET parameters.

So, there you have it. If you want the smallest possible physical size for a QR code which contains a URl, make sure the text is all in capital letters.

#qr #QRCodes