HomeLatest ThreadsGreatest ThreadsForums & GroupsMy SubscriptionsMy Posts
DU Home » Latest Threads » bananas » Journal
Page: 1 2 3 4 5 6 7 Next »

bananas

Profile Information

Member since: Tue Nov 9, 2004, 11:55 PM
Number of posts: 27,509

Journal Archives

Freedom From Logic

http://golem.ph.utexas.edu/category/2012/11/freedom_from_logic.html

November 9, 2012
Freedom From Logic
Posted by Mike Shulman

One of the most interesting things being discussed at IAS this year is the idea of developing a language for informal homotopy type theory. What does that mean? Well, traditional mathematics is usually written in natural language (with some additional helpful symbols), but in a way that all mathematicians can nevertheless recognize as “sufficiently rigorous” — and it’s generally understood that anyone willing to undertake the tedium could fully formalize it in a formal system like material set theory, structural set theory, or extensional type theory. By analogy, therefore, we would like an “informal” way to write mathematics in natural language which we can all agree could be fully formalized in homotopy type theory, by anyone willing to undertake the tedium.

Peter Aczel was the initial advocate of such a thing here, and I think it’s a great idea. Given that computer proof assistants are not really yet sufficiently automated to make formalization of nontrivial arguments palatable to the average mathematician — a situation which I think it will probably take a few decades to overcome, at least — in order for homotopy type theory to make real headway as a foundation for mathematics in the near future, we need a way to do it without computers.

<snip>

Finally, in everyday mathematics, not all the “propositions” we prove are naturally (-1)-truncated! Once my eyes were opened to this, I started to see it everywhere. Most classical mathematicians are deeply programmed to think of proofs as containing no content, in the sense that once you prove a theorem it doesn’t matter what the proof was (a type theorist calls this “proof irrelevance”). But actually, in doing ordinary mathematics it happens to me all the time that I end up writing “by the proof of Lemma 9.3”, because what matters is not just the statement of Lemma 9.3 but the particular proof of it that I gave.

<snip>

Just as intuitionistic logic is more expressive than classical logic because it doesn’t force us to assume the law of excluded middle (but allows us to assume it as an additional hypothesis like any other hypothesis), type theory is allowing us to see a further distinction which was invisible to the classical mind: we aren’t forced to (-1)-truncate all theorems (but we are allowed to, if we so desire, by simply applying the truncation operator).

<snip>

With all the above in mind, I think what I would really like to do is to make a clean break by expunging the notion of “proposition” from the language. In other words, there are only types. Some types are (-1)-truncated. Some types are n-truncated. Some types belong to other modalities. Sometimes we can construct a term in a given type as it stands. Other times we can only construct a term in some truncation of it, or in its reflection into some other modality. (For instance, this is quite a common occurrence for the “classical logic” modality.)

<snip>

Reaction Engines Breakthrough Could Mean Four Hour Flights To Anywhere In The World

Source: Reuters

A small British company with a dream of building a re-usable space plane has won an important endorsement from the European Space Agency (ESA) after completing key tests on its novel engine technology.

Reaction Engines Ltd believes its novel Sabre engine, which would operate like a jet engine in the atmosphere and a rocket in space, could displace rockets for space access and transform air travel by bringing any destination on earth to no more than four hours away.

That ambition was given a boost on Wednesday by ESA, which has acted as an independent auditor on the Sabre test programme.

"ESA are satisfied that the tests demonstrate the technology required for the Sabre engine development," the agency's head of propulsion engineering Mark Ford told a news conference.

<snip>

Read more: http://www.huffingtonpost.com/2012/11/28/reaction-engines-space-plane_n_2204389.html

Elon Musk - the Future of Energy & Transport



http://nasawatch.com/archives/2012/11/video-musk-in-d.html

Video: Musk In-depth Discussion

On November 14 Elon Musk participated in a 90 minute Q&A at the Oxford Martin School with the topic the Future of Energy and Transport. From the abstract, Musk "will talk from his own experiences at the forefront of technology and innovation about what kind of technological transformations are just around the corner and how these can help address the world's critical challenges."


Published on Nov 22, 2012 by 21school

About this event:
http://www.oxfordmartin.ox.ac.uk/event/1402

Webcast:
http://www.oxfordmartin.ox.ac.uk/videos/view/211

MP3 Download:
http://www.oxfordmartin.ox.ac.uk/downloads/podcasts/201211_musk.mp3

MP4 Download:
http://www.oxfordmartin.ox.ac.uk/webcast/201211_musk.mp4

Oxford Martin School,
University of Oxford
www.oxfordmartin.ox.ac.uk


Elon Musk - the Future of Energy & Transport



http://nasawatch.com/archives/2012/11/video-musk-in-d.html

Video: Musk In-depth Discussion

On November 14 Elon Musk participated in a 90 minute Q&A at the Oxford Martin School with the topic the Future of Energy and Transport. From the abstract, Musk "will talk from his own experiences at the forefront of technology and innovation about what kind of technological transformations are just around the corner and how these can help address the world's critical challenges."


Published on Nov 22, 2012 by 21school

About this event:
http://www.oxfordmartin.ox.ac.uk/event/1402

Webcast:
http://www.oxfordmartin.ox.ac.uk/videos/view/211

MP3 Download:
http://www.oxfordmartin.ox.ac.uk/downloads/podcasts/201211_musk.mp3

MP4 Download:
http://www.oxfordmartin.ox.ac.uk/webcast/201211_musk.mp4

Oxford Martin School,
University of Oxford
www.oxfordmartin.ox.ac.uk


"Green Bitumen?!" Nuclear reactors in the tar sands

http://www.dominionpaper.ca/articles/4570

August 27, 2012

"Green Bitumen?!"
Nuclear reactors in the tar sands

by D'Arcy Hande, Mark Bigland-Pritchard


Proponents of nuclear energy are claiming small nuclear reactors in Saskatchewan will make the Alberta tar sands more environmentally friendly, all in an effort to revive the nuclear industry. Photo: Zinta Avens Auzins


SASKATOON—What do you get when you cross a nuclear reactor with a hydraulic shovel-full of tar sands? The answer, according to the Canadian Energy Research Institute, is "Green Bitumen."

The brainchild of the nuclear industry, this novel concept of deploying small modular nuclear reactors (SMRs) to replace natural gas is being sold as a solution to the tar sands' reputation for producing the largest carbon footprint on the planet. Nuclear is being touted as an environmentally friendly, "clean" energy source for the extraction process. But in order to make that claim, one must overlook the substantial carbon emissions in the nuclear "fuel cycle," from mining to ultimate disposal; the risks of weapons proliferation; the toxic radioactive footprint; and the legacy of highly radioactive waste left behind for many generations to come.

<snip>

The nuclear industry, government and academia are pitching "Green Bitumen" to the tar sands industry and anyone else who will listen. Dr. Warren Bell, founding president of the Canadian Association of Physicians for the Environment, sees wide and grave implications for the environment and public health should this message resonate with its target audience.

"The federal and provincial governments are intent on tying the tar sands to nuclear power. Their forlorn hope is that the putative 'greenness' of the latter will counteract the overwhelming 'blackness' of the former," Dr. Bell told The Dominion.

<snip>

Does DOE’s Funding Announcement Mark the End of its Irrational Exuberance for SMRs?

http://allthingsnuclear.org/does-does-funding-announcement-mark-the-end-of-its-irrational-exuberance-for-smrs/

Does DOE’s Funding Announcement Mark the End of its Irrational Exuberance for SMRs?

Ed Lyman, senior scientist
November 21, 2012

On November 20 DOE finally announced that the Babcock and Wilcox Company (B&W) and its “mPower” reactor were the lucky winners of its Funding Opportunity Announcement (FOA) for a cost-sharing program with industry for the design and licensing of “small modular reactors,” or SMRs. Although DOE had originally said the announcement would come in July or August, it decided instead to bury it on Thanksgiving week – not usually a time the agency releases news of which it is particularly proud.

And in fact, the real news is not that a grant was awarded to B&W – this was a near-certainty – but that there was only one winner instead of two. While the initial FOA specified the program was meant to fund “up to two” projects, the widespread expectation was that two grants would be awarded to the pool of four applicants.

<snip>

So what happened to the second grant? One can come up with two theories – either there wasn’t enough money left over once B&W took its cut, or the other applications had so little merit that DOE could not come up with a justification for funding them.

Of the other three applications, one may have been too similar to the B&W concept (the Westinghouse SMR). The other two, NuScale and the Holtec HI-SMUR, are novel designs that have no motor-driven pumps and depend entirely on natural circulation for cooling – frankly, a risky business in view of the uncertainties and challenges of injecting water into overheating reactors and spent fuel pools that were seen during Fukushima. And the credibility of the latter two proposals was recently damaged earlier this month when DOE directed the Savannah River Site (SRS) in South Carolina to stop using funds intended for environmental management to support their development at the site.

But ultimately, the decision may have come down to the commercial prospects for the technologies. ... Based on economies of scale, small reactors will produce more expensive electricity than large reactors, all other factors being equal. ...

<snip>


About the author: Dr. Lyman received his PhD in physics from Cornell University in 1992. He was a postdoctoral research scientist at Princeton University's Center for Energy and Environmental Studies, and then served as Scientific Director and President of the Nuclear Control Institute. He joined UCS in 2003. He is an active member of the Institute of Nuclear Materials Management and has served on expert panels of the Nuclear Regulatory Commission. His research focuses on security issues associated with the management of nuclear materials and the operation of nuclear power plants, particularly with respect to reprocessing and civil plutonium. Areas of expertise: Nuclear terrorism, proliferation risks of nuclear power, nuclear weapons policy


Not mentioned in the article: because the electricity these things generate is so expensive, the main market for them is oil companies - which can use them to melt oil out of tar sands and shale rock.

Generic Lipitor, atorvastatin calcium, recalled over tiny glass particles

Source: CBS News

Ranbaxy Pharmaceuticals Inc. is recalling more than 40 lots of atorvastatin pills -- the generic version of the popular statin Lipitor -- over possible glass contamination.

<snip>

The company's voluntary recall affects certain lot numbers of 10 milligram, 20 milligram and 40 milligram dosage strengths of atorvastatin calcium pills that are packaged in 90- and 500-count bottles. Ranbaxy said the recall is being conducted with knowledge of the U.S. Food and Drug Administration.

A complete list of lot numbers, bottle sizes and dosages can be found on Ranbaxy's website. Patients taking these pills can contact their pharmacy to see if their pills were from affected lots.

<snip>

Earlier this year, the FDA and Ranbaxy settled an ongoing legal battle over questionable manufacturing practices and "data integrity issues" at several of the company's Indian facilities and one located in New York State. A consent decree was filed by the U.S. Department of Justice on behalf of the FDA in which the drug manufacturer agreed to remedy these problems.

<snip>

Read more: http://www.cbsnews.com/8301-204_162-57553697/generic-lipitor-atorvastatin-calcium-recalled-over-tiny-glass-particles/

Happy Thanksgiving!

What are you thankful for?

I'm thankful Obama won!
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=115x200718
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=115x268872

I'm thankful Bob Filner won!
http://www.democraticunderground.com/1014295304

I'm thankful Scott Peters won!
http://www.democraticunderground.com/1014306475

Happy Thanksgiving!

What are you thankful for?

I'm thankful Obama won!
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=115x200718
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=115x268872

I'm thankful Bob Filner won!
http://www.democraticunderground.com/1014295304

I'm thankful Scott Peters won!
http://www.democraticunderground.com/1014306475

Happy Thanksgiving!

What are you thankful for?

I'm thankful Obama won!
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=115x200718
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=115x268872

I'm thankful Bob Filner won!
http://www.democraticunderground.com/1014295304

I'm thankful Scott Peters won!
http://www.democraticunderground.com/1014306475

Go to Page: 1 2 3 4 5 6 7 Next »