Sammy Hassan
25 posts
Sammy Hassan
@SammyHassan_
PhD student at Harvard
Cambridge, MA Katılım Temmuz 2020
159 Takip Edilen184 Takipçiler
I am absolutely thrilled to announce the release of Gemma 2! Today, we're releasing both pre-trained-only and fully post-trained 9B and 27B models. The full technical report is here: goo.gle/gemma2report and it's live *right now* on aistudio.google.com.
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@ShiQingWang4 @zhigangsuo I think it can be great! You questioned a lot of the fundamentals of the subject which was a good learning experience for all of us. Inexperienced students are less likely to do that 😀
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@SammyHassan_ @zhigangsuo You start to wonder whether it is a great idea for one experienced colleague to sit in the class of another to learn a new subject. Teach the “old dog” a new trick….
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@ShiQingWang4 @zhigangsuo Yes it was so much fun! I really enjoyed your discussions with Zhigang
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@ShiQingWang4 @zhigangsuo @Junsoo_twit @jasongsteck Hi Shi-Qing. I’ll be doing material science consulting at exponent.
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I defended my dissertation, entitled 'Fracture Near Interfaces of Disparate Length Scales,' this week. I always enjoy talking about mechanics, but I especially enjoyed expressing gratitude to the people who have made a positive difference in my life in the last 5 years.
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@zhigangsuo Thank you for everything, Zhigang. Words cannot express how grateful I feel for having you as my mentor.
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@Junsoo_twit Yes! Such a repeatable experimental result that warrants a deep dive 😀
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Apple needs to hire more fracture mechanicians. I think that is a fatigue crack growth. Mine is halfway through. @SammyHassan_
Chris Bakke@ChrisJBakke
I’m the VP of Hardware at Apple ($12.4M TC) responsible for making this part that cracks on every charger that we’ve produced over the last 15 years.
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@zhigangsuo @clgschoen Thank you Zhigang! It was such a pleasure being a TF for the class. I learned a lot from you and from interacting with students. It was very fun!
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@clgschoen Thank you. The semester ended last week. I enjoyed thinking through the subject once again.
I have also posted the homework problems along with the schedule. Not all students have all the background. @SammyHassan_ has been a great teaching fellow to help students with homework.
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I’ll be teaching Fracture Mechanics this semester. Here is a lecture-by-lecture schedule, along with my notes.
docs.google.com/document/d/19t…
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Sammy Hassan retweetledi
Dr. Jun He, Vice President of TSMC, will give a seminar entitled
Science behind Chip Manufacturing
hosted by Harvard School of Engineering and Applied Sciences @hseas
The seminar will be in person.
2:00 pm, Monday, 8 May 2023
Pierce Hall 209
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@jasongsteck @Junsoo_twit It’s been a pleasure working with you!
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In particular, thank you to friends and co-first authors, @Junsoo_twit and @SammyHassan_. Your help made this both fun and possible.
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Last Friday, I successfully defended my dissertation, entitled "Fracture of Heterogeneous Soft Materials". Thank you to my committee and everyone who attended!
These 5 years have been blessed with outstanding mentors, collaborators, and friends. Thank you all!
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@samoalfred @zhigangsuo @AditiChak14 Thank you Zhigang. @samoalfred I am happy to discuss mechanics and potential projects at anytime!
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@zhigangsuo @AditiChak14 @SammyHassan_ Thanks Professor. @SammyHassan_ isn't a regular twitter user but I find a way to get across to him.
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The balloon pops, a crack runs along the length of the balloon, and the balloon turns into a strip.
Look at the straight edges of the strip!
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This was a very enjoyable paper to work on! @jasongsteck and I were first puzzled when we analyzed the non-linear elastic stress field around a corner. The illumination came from Fig. 6.
Zhigang Suo@zhigangsuo
In this new paper, @jasongsteck, @SammyHassan_ and I study a common experience: initiation of fracture from a corner of a brittle soft material. doi.org/10.1016/j.jmps…
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@Junsoo_twit @jianyuvli @zhigangsuo @CretonCost @ProfZhaoMIT @NPeppas @DRudolfKing Thank you Jianyu for the question and Junsoo for the answer. To add to Junsoo's answer, in principle even short chains can exhibit rate-depedent toughness if you go fast enough. In our work, our stretch rate was limited by the loading rate of the Instron machine (25mm/s).
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@jianyuvli @zhigangsuo @SammyHassan_ @CretonCost @ProfZhaoMIT @NPeppas @DRudolfKing Hi Jianyu! Thanks for the great question. The toughness is rate-dependent when the chains are extremely long. When these long chains are not densely entangled, the hydrogel becomes too squishy to manipulate as they swell excessively in water.
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In this new paper with @SammyHassan_ @Junsoo_twit, experimental data make us modify the Late-Thomas model.
A hydrogel has rate-independent deformation, but rate-dependent toughness.
@CretonCost @ProfZhaoMIT @NPeppas @DRudolfKing
authors.elsevier.com/a/1dy1-_WmNo%7…
Massachusetts, USA 🇺🇸 English
@DRudolfKing @Junsoo_twit Thank you for sharing your thoughts, Dan. The picture you have is very reasonable. The reason we believe our rate-dependency is governed by the chain length is because of unpublished data we collected that shows this effect in a hydrogel of long chains and little entanglements.
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@Junsoo_twit If you move too fast, the entanglements don’t have time to “slide” and therefore act like fixed entanglements. Slowing down the rate prevents stress from concentrating locally, allowing a larger dissipation zone. We show this effect macroscopically here: onlinelibrary.wiley.com/doi/full/10.10…
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My second paper at Harvard is online at JMPS!
It was such a pleasure to work with @SammyHassan_ and @zhigangsuo!
Zhigang Suo@zhigangsuo
In this new paper with @SammyHassan_ @Junsoo_twit, experimental data make us modify the Late-Thomas model. A hydrogel has rate-independent deformation, but rate-dependent toughness. @CretonCost @ProfZhaoMIT @NPeppas @DRudolfKing authors.elsevier.com/a/1dy1-_WmNo%7…
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Here is a free link to the paper, valid until December 10, 2021: authors.elsevier.com/c/1dy1-_WmNo~1D
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Our paper is now online! We explain the rate-dependent toughness of an elastic hydrogel by a shear lag model. The key, as with all elastic dissipaters, is the length of stress-deconcentration. We show how different stretch rates affect this length and modify the Lake-Thomas model
Zhigang Suo@zhigangsuo
In this new paper with @SammyHassan_ @Junsoo_twit, experimental data make us modify the Late-Thomas model. A hydrogel has rate-independent deformation, but rate-dependent toughness. @CretonCost @ProfZhaoMIT @NPeppas @DRudolfKing authors.elsevier.com/a/1dy1-_WmNo%7…
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Although we use a ceramic-matrix composite to demonstrate this principle, the idea of stress de-concentration is general and far-reaching. We discuss its implications for different synthetic and natural materials in this paper.
Zhigang Suo@zhigangsuo
Brittle materials are all alike; every tough material is tough in its own way. In this paper, we describe how low viscosity leads to high toughness. @SammyHassan_ @Junsoo_twit @CretonCost @ProfZhaoMIT @lin_shaoting @LPamiesOscar @jdolbow @ShengqiangCai
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Sammy Hassan retweetledi
A letter issued by the American Physical Society in support of Professor Gang Chen.
Please kindly retweet.
cdn.fbsbx.com/v/t59.2708-21/…
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@DomelGino @Baohong_Chen @zhigangsuo As mentioned by others, the bag was anisotropic in the vertical vs horizontal direction. We also tried to tear LDPE bags from Target for fun which felt a lot tougher than HDPE. The trend in toughness was also opposite to that of HDPE, i.e they were easier to tear horizontally.
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My housemate @SammyHassan_ and I ruptured some plastic bags tonight. We started with the classical Griffith crack pulled in the vertical direction @Baohong_Chen @zhigangsuo
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