한세희 Sehee Hahn

read and write about tech & more.

[한세희 Sehee Hahn @h32]

IonQ to Acquire Oxford Ionics for a $1.075 Billion Valuation - Quantum Computing Report 이온트랩 기술 기업 2곳 합체 https://t.co/G70mUjgLlQ

[한세희 Sehee Hahn @h32]

Stop saying “I'm free nowadays.” Instead, put it this way; “I am carrying out those ‘not urgent, but important’ things.” from The 7 Habits of Highly Effective Unemplyed.

[한세희 Sehee Hahn @h32]

@slowblogger Yes, history major is useless if you meant it is hard to monetize. I know it from my own experiences. :)

[한세희 Sehee Hahn @h32]

Is is too hard for AI to response the prompts to create images of unconventional mermaids with fish head and human legs? It never gives up the fish tail! #DALL_E #Bing #image_creator

[한세희 Sehee Hahn @h32]

구독 모델, 뉴욕타임스-WSJ은 성공하고, 다른 곳은 힘겨워하고...디지털 미디어 구독 성공 요소는? 라이프스타일 vs informed decision https://t.co/qzPXHi9lqC

[한세희 Sehee Hahn @h32]

Upside down, still alive. Mission ongoing #SLIM https://t.co/SW8A37yTik

[한세희 Sehee Hahn @h32]

@timestripe is a good way to organize your life with the whole sight of your time span from day to day chores to life time goal. see both a tree and forest! calendar, kanban and whiteboard!

[한세희 Sehee Hahn @h32]

https://t.co/0Xfe4m1k7g

[한세희 Sehee Hahn @h32]

https://t.co/QL99h3tTEP

[한세희 Sehee Hahn @h32]

온라인 스크랩 & 읽기 도구 미멕스가 많이 변화되었네요. 과연 기억의 확장 얼마나 가능하게 해 줄지

[Memex.Garden @memexgarden]

Memex is in public beta (again)

We closed down our signups earlier this year when we launched Memex' collaboration features.
Over the past 12 months we've been working hard to polish the product and if you haven't used Memex in a while you may want to try it again.

For quick summary of what we've added last year you can watch the attached video or read on.

Some highlights:
👯‍♂️ Collaboratively curate, annotate and discuss websites, PDFs and videos. (see video)

📣 Share and collaborate with people who don't use the Memex extension with our new web reader.
https://t.co/lrXsAET9cP

🤖 AI assistant to summarise & ask questions about websites, PDFs, YouTube videos and text/video sections.
https://t.co/3qiDdjEgsB

▶️ Video timestamp annotations, including smart notes
https://t.co/iClCX8yLyh

📸 Frame snapshot annotations on Youtube
https://t.co/53DoTesv5w

✍🏽 Annotate illustrations on PDFs
https://t.co/INISHItgSs

💎 Obsidian & Logseq live sync
https://t.co/sSgzrj9ApO

🌆 Image Support for annotations
https://t.co/53DoTesv5w

🌙 Dark & Light mode redesign
https://t.co/jhycOAhzNW

🐦 Use Memex as a CRM for Twitter & Telegram: Organise/search/filter profiles and annotate chat logs
https://t.co/bY6KM1dLSv

+ 200 bug fixes and dozens of quality of life improvements.

What's next?
🔓 Private spaces with email invites (in polish)
📱 Native in-browser annotations & search on mobile (in progress)
🗂️ Nesting Spaces for better organisation (in design)

Transferrable Lifetime Subscription Deal
We've also launched a limited offer for a transferrable lifetime subscription.

For $400 you can use all Memex features until you hopefully die at an old age - and if you don't need it anymore you can gift or sell it to someone else.

We wanted to make our early supporters benefit greatly from the improvements to the product we're going to make even if they stop using Memex.
Our hope is that it'll also help us stay more independent from venture capital pressure as a Steward Owned business.

For more info, check out our website (in our bio)

[Jasper Polak @polak_jasper]

Dunno who made this but it's genius. Why change fails:

[한세희 Sehee Hahn @h32]

이 사진을 @unsplash에서 제공해 주신 @canweallgo 님께 감사드립니다 🎁 https://t.co/UNxcqhB502

[한세희 Sehee Hahn @h32]

초기에 트위터에서 LK-99 열풍에 일조했던 Cote가 회의론으로 전환

[Andrew Côté @Andercot]

LK-99: The Case for Skepticism

By now there's been a number of replications, videos, pre-prints on arxiv, and at-home or at-work attempts to reproduce the original findings of Lee and Kim.

Here's why I'm increasingly skeptical on LK-99 and my reasoning:

#1 - The Videos
There's been a number of videos produced and circulating the internet showing partial levitation or full levitation, the kind of thing you see in cryogenic superconductors that 'quantum lock' or 'flux pin' and float in mid-air.

The issue with all these videos is that the visual behavior is completely indistinguishable from a diamagnetic.

I was initially under the impression that you could not produce stable levitation from two simple dipoles, according to a time-honored theorem from physics by Earnshaw, and so levitation above a single magnet was 'proof positive'.

However, as it turns out, there is a less well-known exception to this rule called Brauenbecker extension which provides a mathematical proof that levitation is possible with a simple diamagnetic in a dipole field so long as the diamagnetic material mass is very small relative to the strength of the magnetic field.

(Note that there are plenty of videos of a diamagnetic floating above a grid of magnets, but those magnets have a more complicated field than a dipole and so Earnshaw's theorem does not apply. Here is the derivation of Brauenbecker's result for the curious: https://t.co/WUGzMdQUTC )

The suspicious thing in the levitation of LK-99 videos is that the 'stable equilibrium point' is directly above the center of the magnet. This is what you'd expect via the Brauenbecker derivation - that the only stable point is in the center. A flux-pinned super conductor could levitate in many different orientations including off to the side of the magnet.

Conclusion - the videos do NOT show flux-pinning.

#2 The Simplest Measurements are Missing

By now there have been several replications of the material by laboratories of professional scientists with high quality equipment that yield a high purity of LK-99, higher purity than the original reports by Lee and Kim.

None of these measurements have accomplished the most direct and obvious result of room-temperature superconductivity, which is zero resistance at room-temperature.

Lee and Kim's original paper had badly formatted plots, not the best choice of plot axes, and in general it was overall rushed to arxiv. They reported absolute resistance but not physical dimensions of the sample, and claimed a resistivity in the text of their article that was on the order of a superconductor but it isn't clear where that calculation came from.

Subsequent teams have published results claiming 'zero resistance' but at 110K - which is great, but not that impressive - tons of materials superconduct at very low temperatures and so it is not indicative of much special about LK-99.

Conclusion - Measurements are the proof and they haven't materialized

#3 - Simulations are suggestive and not predictive

Much of my initial enthusiasm came from reading simulations performed by well-respected scientists like @sineatrix at LBNL and others are University of Boulder Colorado and TU Wien - their results didn't rule out LK-99 entirely! I thought this was incredible.

However, this was always tempered by the knowledge that the physical properties as measured by lab equipment would be soon to follow and support the proposed mechanisms of superconductivity as described in the preprints on simulations. Notably those simulation results are also congruent with other more mundane interpretations like magnetism and diamagnetism, as mentioned by the original authors themselves.

Conclusion - Simulations are suggestive but we don't live in a simulation

~~~~~~~~~

Overall Takeaway:
I first wrote about my initial take on the LK-99 publication in this tweet here: https://t.co/MfreaiUXaO

I expressed a few concerns in that original tweet and so far none of them have been adequately addressed, despite several replication attempts and follow-ups. If this material was the holy grail of materials science then it seems likely at least some of the missing results would have manifested by now.

Summary:
- Videos are explainable by more mundane everyday effects
- Key measurements are missing
- Simulations are nice but we don't live in one.

~~~~~~~~~~

As I've said before I'm deferring any real conclusions until the results of Argonne National Lab, but right now my mental model is:

LK-99 is a diamagnetic semiconductor.

This doesn't change my conviction that ambient-pressure room-temperature superconductors can very well be discovered and manufactured at-scale within our lifetimes, and that such a development would be a watershed moment for humanity.

[한세희 Sehee Hahn @h32]

LK-99: 상온 초전도체 호소물질

[한세희 Sehee Hahn @h32]

Elon Musk defends Soros tweets: 'I'll say what I want' FYI) He already has a lot of money. https://t.co/yPSkqdapmA

[한세희 Sehee Hahn @h32]

Turns out that robots can, but you can't. #GPT #generative_AI

[한세희 Sehee Hahn @h32]

I'm #323 on 🧲리캐치 얼리액세스 👉 https://t.co/ukSC54SJGp

[한세희 Sehee Hahn @h32]

Nothing starts with N and ends with G.

[한세희 Sehee Hahn @h32]

@postsecret "Maybe what I feel about Hong Ye-hyon (person's name) could be love." This doesn't translate exactly the original Korean sentence, but kinda similar. 홍예현 is person's name, but hard to tell if it's a boy a girl.

[한세희 Sehee Hahn @h32]

Do you remember when you joined Twitter? I do! #MyTwitterAnniversary