* Posts by ARaybould

18 posts • joined 28 Mar 2010

Brit rocket boffins Reaction Engines notch up first supersonic precooler test

ARaybould

Inlet Air Temperature

I am pretty sure that, while the inlet ramps on a Concorde's engines did slow down the incoming air, this did not result in cooling, and in fact increased the temperature considerably. One of the purposes of the ramps was pressure recovery, using the kinetic energy of the incoming air to increase its pressure, with a side effect of raising its temperature.

The inlet cones of the SR-71 served the same purpose, and they increased the temperature at the compressor inlet so much that it was the consequent risk of overheating of the engine, not its thrust, that limited its top speed.

In fact, this is probably why the SABRE engine has to be able to cool air from 420°C, as the ambient temperature will be much lower. It is probably not a coincidence that I have seen 427°C quoted as the maximum allowable temperature at the SR-71 compressor inlet (limiting its speed to around Mach 3.3, depending on ambient conditions.)

Hard numbers: The mathematical architectures of Artificial Intelligence

ARaybould

Re: AI - a moving goalpost

Calling the technologies of the 1980s AI was itself a major displacement of the goalposts. The movement you observe now is a drift back to their natural position.

ARaybould

No Point in Fooling Ourselves

It is a little bit self-serving to say that the definition of AI is a work in progress, but also rule out consciousness as a defining issue without discussion or justification. The term AI has been so abused that the retronym 'generalized AI' had to be created to recover the original meaning, and we don't need to go down that road again.

This confusion has consequences: for one thing, the people who are concerned about the existential threat of conscious AI are simply not understood by those who think of AI as being something like Cortana.

I am not one of those people who dismiss the current results of AI research as 'merely' some variant of database lookup or rules application, and I agree that the translation between a language-pair not explicitly trained for is an exciting development. For example, we know that neural networks, by design, create 'hidden' representations, so one thing I am wondering is whether Chomsky's deep grammar will at some point be experimentally verified. Whether, or how close, this development is to being called AI is not high on my list of interesting questions about it.

Whether current methods will lead to something that can reasonably be called AI remains to be seen. Premature claims of the achievement of AI (such as the silly claim of the Turing test being passed by a chatbot, last year) are or will be only pointless self-deception.

Soz, folklore fans! Negligence, not Nessie, sank WWI German sub

ARaybould

Christmas Tree

> Of course, you have to watch it...

There is quite an incentive to do that.

Japan's Hitomi space 'scope bricked, declared lost after software bug

ARaybould

Re: 'Paranoid Programming Practices'

There's 'Safeware: System Safety and Computers' by Nancy Leveson.

'Devastating' bug pops secure doors at airports, hospitals

ARaybould

Re: The service runs as root?

Don't pick on the programmers - no-one taught them anything about security.

12 simple rules: How Ted Codd transformed the humble database

ARaybould

Not so Simple

To someone approaching the relational model by learning SQL, it might superficially look like just 'data in tables', but it is not that simple. I recall being a meeting in which the DBAs proudly unveiled their schema for a rewrite of their company's customer and order database. It was fully normalized, they claimed, but it turned out that they had packed a bunch of repeating groups into strings. What they thought was being clever merely revealed the superficiality of their understanding, and this decision caused no end of problems.

BTW, I am aware that denormalization may be the right design choice, but that is beside the point here.

ARaybould

Re: Mainframe yes.. Website no.

The problem of SQL injection attacks has nothing to do with the relational model or even its implementations (given that secure ways to bind data exist), and everything to do with amateurism in web development.

Bjarne Again: Hallelujah for C++

ARaybould

Dr. Pangloss

"...because it is Dr S, and because there is a slight, defensive hint of Dr P-for-Pangloss about him..."

I have noticed this too: he manages to explain any aspect of C++ as exactly what you want, or at least the only sensible option. While reading 'The Design and Evolution of C++', I realized how he does this: at the start, he outlines a number of goals that are each worthy, but which are, in many cases, mutually antagonistic. He is then able to pick a subset of those goals to justify almost any aspect of the language.

I sometimes wonder if a simpler, yet equally capable language could be achieved if one or more of these goals could be dropped, and I think the best candidate would be the 'superset of C' one, though I understand the reason for it.

While C++ can be frustrating, there are many cases where it is the best choice. It is also a language, like Smalltalk, Lisp and its variants, assemblers, and C itself, that can teach you a lot about programming in general. C++ and Objective-C came along at about the same time, and the latter was sometimes described as 'more object-oriented', so I sometimes wondered if it was a better choice, until I actually got to use it...

Ice age end was accelerated by CO2

ARaybould

Re: Primary causes?

From which one of the voices in your head did you hear that?

30-year-old global temperature predictions close to spot-on

ARaybould

Re: But how many 1980's papers were wrong?

So the existence of unsuccessful models (and failed experiments, for that matter) bring into doubt the successful ones? That's not the way the scientific method works; it is designed to pay a great deal of attention to what works, and the gold standard in that regard is successful prediction. Contrary to its presentation in introductory texts, the history of science is not a simple progression of successful experiments, valid observations and correct deductions, and if the failures counted against the successes, science would have long ago collapsed under the weight of accumulated falsehoods and idle speculation.

Iran spy drone GPS hijack boasts: Rubbish, say experts

ARaybould
Thumb Down

What the Paper Actually Claims

"We will show, for example, that any number of receivers can easily be spoofed to one arbitrary location".

The problems considered in this paper are harder than simply persuading a naive GPS user (one that is not attempting to determine if it is being spoofed) that it is somewhere other than it actually is. They include such problems as doing so without losing lock, and spoofing a number of spatially-separated receivers such that their apparent mutual separation conforms with reality. They conclude that "spoofing detection based on lock loss has two disadvantages: (i) strong attackers can achieve a seamless satellite-lock takeover, and (ii) lock loss can occur due to natural causes" and so propose the use of multiple, separated receivers as the basis of a spoofing-detection mechanism.

The actual content of this paper, therefore, does not justify the claim in the Register article's headline.

Has your account been pwned? New website will tell you

ARaybould

Don't read, or don't understand?

You are replying to a post that mentions the SHA 512 hash option, which appears in the first paragraph on the web site. Did you not read down that far in either of these, or do you think that the hash is personally-identifying or has some other value to a third party?

Don't bother with that degree, say IT pros

ARaybould
Thumb Down

Indictment of Education

This is the predictable consequence of the dumbing-down of higher education:

http://www.lambdassociates.org/blog/decline.htm

http://www.theregister.co.uk/2008/09/13/verity_stob_open_university/

Programming is just the second step in Comp. Sci. (after discrete mathematics & logic - but I get the impression that this foundation is being skimped on as 'too difficult'), so when you get graduates who cannot even program, something is wrong.

Finance software bug causes $217m in investor losses

ARaybould

License Terms

I would like to know if this particular product had a typical "we are not responsible for anything that happens" EULA. My guess is that it was, but a combination of hiding a known problem and the specifics of the securities law trumped those claims.

I was once told by a development manager that his former employer, a producer of medical software, did not use bug-detecting software because they would be responsible for any bug found but not fixed. The time for the principle of "if you accept payment for it, you also accept responsibility" is long overdue.

Fukushima fearmongers are stealing our Jetsons future

ARaybould

Hysteria

I take it that the "hysteria now completely disconnected from reality" would be Mr. Page's belief in a global media conspiracy to spread panic. There is no shortage of responsible, informed articles for those who are looking for them.

Fukushima on Thursday: Prospects starting to look good

ARaybould

Reasonable answers to the wrong questions

Higlander's case is that the plant staff has done an excellent job, given the circumstances, and I do not wish to argue with that. The issue, however, is whether inadequate preparation and complacency exacerbated those circumstances and created significant additional risk, turning what could have been a demonstration of the safety of nuclear power into a reason for continuing concern over how it is managed.

He says that hindsight is easy, but in this case, so too would foresight have been. Earthquakes and tsunamis of this magnitude and greater are expected, and their consequences are well-known; as another commenter pointed out, the 2004 Indonesian tsunami should have acted as a wakeup call, even if Tokyo Electric Power had underestimated the risk to that point.

We also have credible reports from the Wall Street Journal that TEPCO delayed taking effective action to stabilize the situation out of concern for its investment in the plant. If confirmed, this would also confirm that TEPCO was unable to manage the crisis effectively, as prioritization of concerns and decisive action are important parts of crisis management.

Highlander questions whether US plants are as well-prepared as were the Japanese ones. It is simply a logical error, however, to think that any alleged lack of preparedness elsewhere justifies TEPCO’s lack of sufficient readiness: it is the wrong measuring-stick. Furthermore, Highlander has apparently missed the irony in his questions about nuclear safety elsewhere, given his pro-nuclear stance.

I, too, am unimpressed by the quality of journalism. One issue is that the media failed to pick up clues, from the factual evidence, that TEPCO’s public assessment of the state of the plant was repeatedly and unrealistically optimistic, so the bias has not been uniformly pessimistic. Nevertheless, I am prepared to accept that is has been pessimistic on balance, but, once again, it would be a logical error to conclude that there is consequently nothing to be concerned about.

Mr. Page’s questioning of apocalyptic, disproportionate and uninformed reporting is valuable, but his unfortunate practice of responding to speculative, biased editorializing in a like manner has robbed him of the chance to be the voice of reason here, and puts him in the same camp as the people he claims to despise.

Even if things turn out as well as Mr. Page predicts, it does not mean that concern is unwarranted. For every technological disaster, there are an order of magnitude or more of incidents that betray the risk without themselves turning disastrous, and there are risks that are predictable even if they have not been realized yet. As a former worker in the nuclear industry who believes it could be our best response to global warming, I am concerned by the frequency with which that industry tends to downplay these warnings. TEPCO’s failings do not, of course, prove that other operators are unprepared, but there is other evidence on that issue.

US Navy plans self-building floating fortresses

ARaybould

A Century Ago

Type your comment here — plain text only, no HTML

Admiral Sir Percy Scott was one of the most most inventive and iconoclastic British naval officers in the decades leading to WW1, though overshadowed in history by Jackie Fisher. Early in that war he differered with Fisher over the value of battleships, saying that they were not cost-effective, being hugely expensive and too vulnerable to aircraft and submarines. Instead, he proposed developing aircraft carriers that could be used for commercial shipping in peacetime. Given the state of aviation at that time, his proposal looks impractical, but history proved his analysis to be correct. ( "Fifty Years in the Royal Navy" http://freepages.genealogy.rootsweb.ancestry.com/~pbtyc/50_years/FP.html )

Biting the hand that feeds IT © 1998–2019