Yes you will have burned calories but you will have done no work on the wall. The work performed will have been within your body caused by the contraction of muscles. The energy expended will have been converted to heat, presumably now lost to the environment through your skin if you're still alive;-)
If you want to consider all forces and energy transfers within a human body when pushing against a wall, there's a lot to consider - it's far simpler to assume the body is rigid and has no internal structure that you need to be concerned about - in your example perhaps think of a rigid body leaning against a wall, which will impart a force but does not expend energy. In this case we would only need to consider mechanical properties of the system rather than the thermodynamic properties that apply to all real-world systems.
Of course if you are a biologist it might be valid to look at the the energy expended pushing against a stationary wall for an hour. In this case they might want to consider the the source of the energy (chemical), how forces act on the skeleton, the mass of limbs etc - not very useful though if you want to understand fundamental concepts of physics.
Reading through the discussion above and below, it's clear that posters are talking about different systems - this is why the first thing an applied mathematician or physicist does is to draw a diagram, and to state any assumptions. For example I think gbutler69 was talking about a system with the "hand" moving in a circle to impart a force to maintain the kinetic energy of the rock, where KE was being lost to air friction, and the responders were assuming a frictionless system with a rigid, fixed "hand".
To prevent a similar flamewar I should mention that in my example above, the rigid post is attached to the ground, which is also rigid and has infinite mass;-)
Now, what are all the FORCES? What's that tug I feel on my hand that I have to exert energy to overcome? Oh, that's the CENTRIFUGAL FORCE my hand is experiencing.
Perhaps I'm going off the original point of the discussion a bit, but since this is all about understanding physics I thought I should point out that you do not need to exert energy to "overcome" a force. It's only if that force does work that energy is expended. Replace your hand with a rigid post and it will still experience a force, though it clearly doesn't expend energy.
If you would have asked me how it would react as it rolled faster and faster, I would have just assumed it would have gotten "rounder" and possibly larger (elastic) due to centrifugal force.
And I'd think for a suitably low coefficient of friction between the band and the ground you'd have been right.
How about reading TFA? This is not an invasion of privacy at all. It doesn't record any personal data.
If they have access to URLs they have access to anything sent via a GET HTTP request. Are you suggesting that there aren't any websites that collect personal data via GET requests?
I agree it's not clear - I took "other parties" to mean legal entities outside the organization, as in the legal definition of "third party". So my reading is that an employee would not be another party.
The definition of propagation makes no mention of "other parties" (it uses "others") and I'd agree that copying within an organization does appear to be covered within that definition as copyrights are required to allow this.
So I read the definition of conveying to be a subset of propagation that specifically excludes intra-organization copying.
Unfortunately the license doesn't provide definitions for terms like "other parties" or "others" so I guess there will be differences of opinion as long as GPLv3 is relevant - which is a shame for such an important license.
Does the GPL require that source code of modified versions be posted to the public?
The GPL does not require you to release your modified version, or any part of it. You are free to make modifications and use them privately, without ever releasing them. This applies to organizations (including companies), too; an organization can make a modified version and use it internally without ever releasing it outside the organization.
But if you release the modified version to the public in some way, the GPL requires you to make the modified source code available to the program's users, under the GPL.
Thus, the GPL gives permission to release the modified program in certain ways, and not in other ways; but the decision of whether to release it is up to you.
The definition of propagate you've quoted is relevant, though does not in itself mean much without looking at the context in which that definition is used e.g.
You may make, run and propagate covered works that you do not convey, without conditions so long as your license otherwise remains in force. You may convey covered works to others for the sole purpose of having them make modifications exclusively for you, or provide you with facilities for running those works, provided that you comply with the terms of this License in conveying all material for which you do not control copyright. Those thus making or running the covered works for you must do so exclusively on your behalf, under your direction and control, on terms that prohibit them from making any copies of your copyrighted material outside their relationship with you.
Conveying under any other circumstances is permitted solely under the conditions stated below. Sublicensing is not allowed; section 10 makes it unnecessary.
Where conveying is defined as
To “convey” a work means any kind of propagation that enables other parties to make or receive copies. Mere interaction with a user through a computer network, with no transfer of a copy, is not conveying.
So in other words an organization can distribute copies of their own code within the organization without the requirement for that code to be licensed under the terms of the GPL. It's only when the work is conveyed (i.e. propagated to another party) that there are additional conditions, and if that other party is a subcontractor, the conditions don't apply.
The license really needs to be read as a whole rather than as selected quotes though, as there are quite a few dependencies between sections.
Though dioxins are currently ubiquitous much of the dioxin level in the environment is a result of man's activities e.g. paper-making, pesticides etc, so in theory could be reduced.
Indexes on fields with low cardinality doesn't help much, unless you have bitmap indexes.
This is a misunderstanding that often seems to be repeated - what is more important is the distribution of values, so for example select * from foo where status = 'UNPROCESSED' will make efficient use of a standard b-tree index on status even where status can only be PROCESSED|UNPROCESSED, _if_ the number of rows returned is small compared to the total number of rows in the table. If the field has low-cardinality and an even distribution of values you are correct.
This is a very relevant point. I think the answer is that you can only tell whether your data is normalized after referring to the system requirements, and even then 2 designers will come up with 2 different models.
For example your design for customer may be fine if you will only envisage selling to individuals in the US, but what if you are dealing with corporations? Do you need to be able to separate out billing, delivery addresses or people? To what extent do you need to model the organizational structure within your customers? Do you need to hold a history of customer information or is it OK to overwrite the address with the current address if someone moves house? What happens if someones name changes e.g. through marriage or obtaining a doctorate degree? And if you need to send out invoices, you'll probably need an immutable version of customer data for legal audit purposes.
In my experience, the answers to some of these questions will not necessarily be clear initially and typically a client will not be able to specify all these requirements without help. It also requires making judgment calls. Which is where we come in as database designers and IMO makes it a fascinating role.
Of course we can go too far and come up with a design such as
thing (id, thing_type_id, name, value)
thing_type (id, name, value)
etc,
or even store all the business logic in the database.
This can be perfectly valid 3NF and satisfy all business requirements, but there might be one or 2 implementation issues;-)
Back when those books were written, disk was expensive and not cached, RAM was very expensive, and machines had terrible I/O bottlenecks. Normalization is critical under these circumstances for maximum performance.
Normalization has _nothing_ to do with performance. In relational DB design, performance is usually considered only after you have a normalized model at which point you it's common to denormalize for performance and other implementation-specific reasons.
The parent's first link gives a good description of the purposes of normalization.
Today, these normalization techniques will increase performance but not as much as you might think. Really it is best to concentrate efforts elsewhere, especially for a one-person shop.
As the submitter looks to be using RDBMSs, a knowledge of normalization and relational database design should be required I 'd have thought. However, if their systems were designed around ORDBMS (your posts hint that this is your background) the DB design issues would be different, but the summary doesn't suggest this is the case.
Chances of infection via cats are really minuscule; we do big deal of it because when it happens at the wrong time to a wrong person (pregnant woman; think of the children!) the results catch attention.
Overall, cats most likely should be thanked by great contribution to our civilization - for a few thousand years they guard our supplies.
BTW, up to a certain point (not exceeding certain period of smoking / quiting quickly enough - basically mid-20's) the rates of illnesses associated with smoking are practically identical for non)never)-smokers and (ex)smokers.
This isn't clear to me - are you saying we should, or shouldn't be worried about sharing a joint with a cat?
I personally believe that almost everyone is capable of understanding these simple concepts, they just can't be bothered to think.
Or perhaps you can't imagine that some people gain benefits from taking a less risk-averse attitude towards life than you appear to have. Just a thought.
Though you make some good points Modern Art existed long before Duchamp's Fountain.
I guess it depends on what the definition of Modern Art is but if you take it to mean art that is experimental, innovative and rejects convention, the 1800's were the beginning of Modern Art. Manet's nude, Olympia (1863) is a good example - not only does he reject aesthetic concerns, the subject is a prostitute rather than the conventional Venus or goddess.
Duchamp's Fountain really belongs to a branch of Modern Art, Dadaism which is more about questioning the whole concept of art itself.
Whilst I'm sure there are great discoveries to come from gene and synthetic life technologies, I feel it would be a mistake for us to dismiss the benefits of research into plant-based medicines.
Millions of lives have been saved, and are still being saved by the use of plant-derived medicines which include anti-malarials, analgesics, anti-cancer drugs, steroids etc.
It may be a bit hit-and-miss looking for plant extracts that have pharmacological properties but it has been proven to be an effective way of discovering and/or producing new drugs so why dismiss it? Incidentally, it's not always a totally random process - researchers use the knowledge of local healers (or "witch doctors" as you call them) to identify candidate plants for research, or look at plants that have biological effects on other animals etc.
One day we might have the knowledge and skills you hope for, but until then, we'd be missing a big opportunity if we didn't do our best to investigate the properties of plants we have access to right now.
There's a reason that nobody bothered to classify all those bugs in the amazon... who cares. As long as swatting them kills them, a bug is a bug.
Unless it secretes the cure for cancer or something, it's just not a big deal.
However the bug you've just killed might just happen to be the sole pollinator of a plant that is a cure for cancer. You just don't know until you've studied them.
I find it hard to believe that this could be brewed naturally, i.e. using yeast to ferment the liquor. I find it hard to believe that a yeast can live in 50% alcohol, 27% was really pushing the limits.
I'd also find it hard to swallow a 50% A.B.V beer.
The biggest issue I see is the cost of running your server. I'm sure some people here on/. run their own servers. Have you every stopped to think how much it is costing you?
It's not as much as your article suggests (from Google cache - site is down).
Using your figures of 13W @ £0.10 per kW/h we get 0.1*13/1000*24*365 which comes out to £11.39, not the £1139 you quote.
So long as craft need to contain the fuel and mechanism for escaping earth's gravity, they will always be relatively expensive. The problem as I see it is that it currently costs as much to send 1kg of cheap supplies into orbit as it does 1kg of high-tech or human as we're using the same technologies. Why do we need super-reliable craft when sometimes all we need to do is transport fuel, oxygen or food? If we can get the cost of craft for delivering supplies into orbit low enough we shouldn't care if a high proportion of launches fail so no need for expensive and heavy fail-safe systems.
Perhaps we should be looking at some way of firing projectiles into orbit as then all we need to transport is the supply itself and its container? Then we might start to get near your $200/kg target.
Um... tundra is permanently frozen ground. Not a lot of mosquitoes can lay their eggs in a puddle of ice.
More accurately, tundra is permanently frozen subsoil. In most areas the top layer of soil melts each summer, and due to the impermeable permafrost layer beneath, tundra areas tend to be very boggy.
I don't have to imply he's the antichrist anymore. He admitted there has been no warming in 15 years on the BBC.
This is not what he said, he said that the warming trend since 1995 is not statistically significant at the 95% level (which is not surprising when looking at trends in a noisy system when you have only 15 data points).
If you want to see a full transcript rather than the misleading reporting on many news sites, here's a link:
Slashdot Mirror
Yes you will have burned calories but you will have done no work on the wall. The work performed will have been within your body caused by the contraction of muscles. The energy expended will have been converted to heat, presumably now lost to the environment through your skin if you're still alive ;-)
If you want to consider all forces and energy transfers within a human body when pushing against a wall, there's a lot to consider - it's far simpler to assume the body is rigid and has no internal structure that you need to be concerned about - in your example perhaps think of a rigid body leaning against a wall, which will impart a force but does not expend energy. In this case we would only need to consider mechanical properties of the system rather than the thermodynamic properties that apply to all real-world systems.
Of course if you are a biologist it might be valid to look at the the energy expended pushing against a stationary wall for an hour. In this case they might want to consider the the source of the energy (chemical), how forces act on the skeleton, the mass of limbs etc - not very useful though if you want to understand fundamental concepts of physics.
Reading through the discussion above and below, it's clear that posters are talking about different systems - this is why the first thing an applied mathematician or physicist does is to draw a diagram, and to state any assumptions. For example I think gbutler69 was talking about a system with the "hand" moving in a circle to impart a force to maintain the kinetic energy of the rock, where KE was being lost to air friction, and the responders were assuming a frictionless system with a rigid, fixed "hand".
To prevent a similar flamewar I should mention that in my example above, the rigid post is attached to the ground, which is also rigid and has infinite mass ;-)
Now, what are all the FORCES? What's that tug I feel on my hand that I have to exert energy to overcome? Oh, that's the CENTRIFUGAL FORCE my hand is experiencing.
Perhaps I'm going off the original point of the discussion a bit, but since this is all about understanding physics I thought I should point out that you do not need to exert energy to "overcome" a force. It's only if that force does work that energy is expended. Replace your hand with a rigid post and it will still experience a force, though it clearly doesn't expend energy.
If you would have asked me how it would react as it rolled faster and faster, I would have just assumed it would have gotten "rounder" and possibly larger (elastic) due to centrifugal force.
And I'd think for a suitably low coefficient of friction between the band and the ground you'd have been right.
Oh yes Manchester ... now if we could only harness the kinetic energy of the falling rain over Manchester we'd be able to power the world!
This kinetic energy gets converted into heat when the rain hits the ground. So now you want the people of Manchester to be cold as well as wet.
How about reading TFA? This is not an invasion of privacy at all. It doesn't record any personal data.
If they have access to URLs they have access to anything sent via a GET HTTP request. Are you suggesting that there aren't any websites that collect personal data via GET requests?
I agree it's not clear - I took "other parties" to mean legal entities outside the organization, as in the legal definition of "third party". So my reading is that an employee would not be another party.
The definition of propagation makes no mention of "other parties" (it uses "others") and I'd agree that copying within an organization does appear to be covered within that definition as copyrights are required to allow this.
So I read the definition of conveying to be a subset of propagation that specifically excludes intra-organization copying.
Unfortunately the license doesn't provide definitions for terms like "other parties" or "others" so I guess there will be differences of opinion as long as GPLv3 is relevant - which is a shame for such an important license.
Your conclusion appears to be at odds with the FAQ on the GNU website Frequently Asked Questions about the GNU Licenses
Does the GPL require that source code of modified versions be posted to the public?
The GPL does not require you to release your modified version, or any part of it. You are free to make modifications and use them privately, without ever releasing them. This applies to organizations (including companies), too; an organization can make a modified version and use it internally without ever releasing it outside the organization.
But if you release the modified version to the public in some way, the GPL requires you to make the modified source code available to the program's users, under the GPL.
Thus, the GPL gives permission to release the modified program in certain ways, and not in other ways; but the decision of whether to release it is up to you.
The definition of propagate you've quoted is relevant, though does not in itself mean much without looking at the context in which that definition is used e.g.
You may make, run and propagate covered works that you do not convey, without conditions so long as your license otherwise remains in force. You may convey covered works to others for the sole purpose of having them make modifications exclusively for you, or provide you with facilities for running those works, provided that you comply with the terms of this License in conveying all material for which you do not control copyright. Those thus making or running the covered works for you must do so exclusively on your behalf, under your direction and control, on terms that prohibit them from making any copies of your copyrighted material outside their relationship with you.
Conveying under any other circumstances is permitted solely under the conditions stated below. Sublicensing is not allowed; section 10 makes it unnecessary.
Where conveying is defined as
To “convey” a work means any kind of propagation that enables other parties to make or receive copies. Mere interaction with a user through a computer network, with no transfer of a copy, is not conveying.
So in other words an organization can distribute copies of their own code within the organization without the requirement for that code to be licensed under the terms of the GPL. It's only when the work is conveyed (i.e. propagated to another party) that there are additional conditions, and if that other party is a subcontractor, the conditions don't apply.
The license really needs to be read as a whole rather than as selected quotes though, as there are quite a few dependencies between sections.
Though dioxins are currently ubiquitous much of the dioxin level in the environment is a result of man's activities e.g. paper-making, pesticides etc, so in theory could be reduced.
If it's made of muscle fibre I'm not sure I'd want to be in it when the electrical wiring develops a fault.
Indexes on fields with low cardinality doesn't help much, unless you have bitmap indexes.
This is a misunderstanding that often seems to be repeated - what is more important is the distribution of values, so for example select * from foo where status = 'UNPROCESSED' will make efficient use of a standard b-tree index on status even where status can only be PROCESSED|UNPROCESSED, _if_ the number of rows returned is small compared to the total number of rows in the table. If the field has low-cardinality and an even distribution of values you are correct.
This is a very relevant point. I think the answer is that you can only tell whether your data is normalized after referring to the system requirements, and even then 2 designers will come up with 2 different models.
For example your design for customer may be fine if you will only envisage selling to individuals in the US, but what if you are dealing with corporations? Do you need to be able to separate out billing, delivery addresses or people? To what extent do you need to model the organizational structure within your customers? Do you need to hold a history of customer information or is it OK to overwrite the address with the current address if someone moves house? What happens if someones name changes e.g. through marriage or obtaining a doctorate degree? And if you need to send out invoices, you'll probably need an immutable version of customer data for legal audit purposes.
In my experience, the answers to some of these questions will not necessarily be clear initially and typically a client will not be able to specify all these requirements without help. It also requires making judgment calls. Which is where we come in as database designers and IMO makes it a fascinating role.
Of course we can go too far and come up with a design such as thing (id, thing_type_id, name, value) thing_type (id, name, value) etc, or even store all the business logic in the database. This can be perfectly valid 3NF and satisfy all business requirements, but there might be one or 2 implementation issues ;-)
I don't have an answer, it's just not fair. :-(
Yes, it's not fair. But it can very satisfying.
Back when those books were written, disk was expensive and not cached, RAM was very expensive, and machines had terrible I/O bottlenecks. Normalization is critical under these circumstances for maximum performance.
Normalization has _nothing_ to do with performance. In relational DB design, performance is usually considered only after you have a normalized model at which point you it's common to denormalize for performance and other implementation-specific reasons.
The parent's first link gives a good description of the purposes of normalization.
Today, these normalization techniques will increase performance but not as much as you might think. Really it is best to concentrate efforts elsewhere, especially for a one-person shop.
As the submitter looks to be using RDBMSs, a knowledge of normalization and relational database design should be required I 'd have thought. However, if their systems were designed around ORDBMS (your posts hint that this is your background) the DB design issues would be different, but the summary doesn't suggest this is the case.
IQ has a huge correlation with success".
Is this true in societies where success is not at least partially dependent on the ability to pass tests?
Chances of infection via cats are really minuscule; we do big deal of it because when it happens at the wrong time to a wrong person (pregnant woman; think of the children!) the results catch attention.
Overall, cats most likely should be thanked by great contribution to our civilization - for a few thousand years they guard our supplies.
BTW, up to a certain point (not exceeding certain period of smoking / quiting quickly enough - basically mid-20's) the rates of illnesses associated with smoking are practically identical for non)never)-smokers and (ex)smokers.
This isn't clear to me - are you saying we should, or shouldn't be worried about sharing a joint with a cat?
I personally believe that almost everyone is capable of understanding these simple concepts, they just can't be bothered to think.
Or perhaps you can't imagine that some people gain benefits from taking a less risk-averse attitude towards life than you appear to have. Just a thought.
It's not easy for a bank robber to escape on a duck.
Are you sure? AFAIK no bank robber has ever been caught when escaping on a duck.
His message was basically, "art is crap".
I seem to remember his exact words were "The cake is a lie".
Though you make some good points Modern Art existed long before Duchamp's Fountain.
I guess it depends on what the definition of Modern Art is but if you take it to mean art that is experimental, innovative and rejects convention, the 1800's were the beginning of Modern Art. Manet's nude, Olympia (1863) is a good example - not only does he reject aesthetic concerns, the subject is a prostitute rather than the conventional Venus or goddess.
Duchamp's Fountain really belongs to a branch of Modern Art, Dadaism which is more about questioning the whole concept of art itself.
Whilst I'm sure there are great discoveries to come from gene and synthetic life technologies, I feel it would be a mistake for us to dismiss the benefits of research into plant-based medicines.
Millions of lives have been saved, and are still being saved by the use of plant-derived medicines which include anti-malarials, analgesics, anti-cancer drugs, steroids etc.
It may be a bit hit-and-miss looking for plant extracts that have pharmacological properties but it has been proven to be an effective way of discovering and/or producing new drugs so why dismiss it? Incidentally, it's not always a totally random process - researchers use the knowledge of local healers (or "witch doctors" as you call them) to identify candidate plants for research, or look at plants that have biological effects on other animals etc.
One day we might have the knowledge and skills you hope for, but until then, we'd be missing a big opportunity if we didn't do our best to investigate the properties of plants we have access to right now.
There's a reason that nobody bothered to classify all those bugs in the amazon... who cares. As long as swatting them kills them, a bug is a bug.
Unless it secretes the cure for cancer or something, it's just not a big deal.
However the bug you've just killed might just happen to be the sole pollinator of a plant that is a cure for cancer. You just don't know until you've studied them.
I find it hard to believe that this could be brewed naturally, i.e. using yeast to ferment the liquor. I find it hard to believe that a yeast can live in 50% alcohol, 27% was really pushing the limits.
I'd also find it hard to swallow a 50% A.B.V beer.
The biggest issue I see is the cost of running your server. I'm sure some people here on /. run their own servers. Have you every stopped to think how much it is costing you?
It's not as much as your article suggests (from Google cache - site is down).
Using your figures of 13W @ £0.10 per kW/h we get 0.1*13/1000*24*365 which comes out to £11.39, not the £1139 you quote.
So long as craft need to contain the fuel and mechanism for escaping earth's gravity, they will always be relatively expensive. The problem as I see it is that it currently costs as much to send 1kg of cheap supplies into orbit as it does 1kg of high-tech or human as we're using the same technologies. Why do we need super-reliable craft when sometimes all we need to do is transport fuel, oxygen or food? If we can get the cost of craft for delivering supplies into orbit low enough we shouldn't care if a high proportion of launches fail so no need for expensive and heavy fail-safe systems.
Perhaps we should be looking at some way of firing projectiles into orbit as then all we need to transport is the supply itself and its container? Then we might start to get near your $200/kg target.
Um... tundra is permanently frozen ground. Not a lot of mosquitoes can lay their eggs in a puddle of ice.
More accurately, tundra is permanently frozen subsoil. In most areas the top layer of soil melts each summer, and due to the impermeable permafrost layer beneath, tundra areas tend to be very boggy.
As a result, Tundra areas can have some of the highest concentrations of mosquitoes in the world: http://www.athropolis.com/arctic-facts/fact-mosquito.htm
I don't have to imply he's the antichrist anymore. He admitted there has been no warming in 15 years on the BBC.
This is not what he said, he said that the warming trend since 1995 is not statistically significant at the 95% level (which is not surprising when looking at trends in a noisy system when you have only 15 data points).
If you want to see a full transcript rather than the misleading reporting on many news sites, here's a link:
http://news.bbc.co.uk/1/hi/sci/tech/8511670.stm (Question B)