Yes, of course you're right. It's the AREA of the disk, multiplied by the velocity, which determines how much air is moved at what rate, which equals how much thrust is created (Newton's third law). I typed it as circumference rather than area.
What I didn't go into was a consideration with real props which brings it closer to directly proportional, so the actual real-life performance is in between the area and the circumference. The inner part of the blade is of course moving slower than the tips, in terms of linear speed. In other words, if the rotor tips are moving through the air at 400MPH, halfway toward the hub it's only slicing through the air at 200MPH. So the portion of the rotor which is delivering maximum power is at the ends, measured by the circumference.
Does that make sense? The total area is proportional to r^2, but the area of blade working at full speed is proportional to just r. Meaning the total thrust is between X * r and X * r^2.
Your correction points out why large rotorcraft normally use one lifting rotor rather than multiple as hobby craft often do. A single 40 foot rotor has twice the swept area of the two 20-foot rotors which would fit on the same airframe. Of course, when you need rotor too big to build and affix to the airframe, such as a heavy-lift copter, you may end up with tandem rotors simply because a 120' rotor is Impractical.
There are similarities and differences. Before the EU was formed, each of the 28 countries already had their own approval process. After the formation of the EU, which is principally an economic and trade alliance, a drug approved in ANY EU country could be sold in ALL EU countries. Therefore a pharmaceutical company could choose which of the 28 countries would likely approve the drug most easily / quickly / cheaply. Commonly, a pharmaceutical company will apply in two or three countries at once and see which one approves it first.
Some drugs are now required to go through one of several centralized EU approval processes instead - and there are four for them to choose from. Being run by the EU, the heritage of these agencies is based on promoting commerce between EU countries - the EU is not focused on consumer protection and safety.
In the US, a maker has to get approval from the FDA. They don't get to choose different agencies to seek approval from. The DA started as a consumer protection agency, trying to make sure drugs were safe. Later, they got mandate to make sure they are effective. The FDA doesn't have the heritage of coming from an organization trying to promote commerce, like the EU does.
Therefore historically it's been easier and cheaper to get drugs approved in Europe than in the US. Europeans got cheaper medicines faster, Americans got better, more expensive medicine. (The difficult and expensive FDA process isn't a total waste).
In the last few years, there has been pressure on both sides of the Atlantic to be more like the other guys. Americans want cheaper drugs, sooner. Europeans want want better, safer drugs. I guess the grass is always greener on the other side of the fence. So each process has become more like the other and the difference isn't as extreme as it once was.
For an actuator disk of area A, with induced velocity v at the rotor disk, and with p as the density of air, the mass flow rate m through the disk area is:
m =pAv
By conservation of mass, the mass flow rate is constant across the slipstream both upstream and downstream of the disk (regardless of velocity). Since the flow far upstream of a helicopter in a level hover is at rest, the starting velocity, momentum, and energy are zero. If the homogeneous slipstream far downstream of the disk has velocity w, by conservation of momentum the total thrust T developed over the disk is equal to the rate of change of momentum, which given zero starting velocity is:
T=mw
Because tip velocity can't exceed c, w is limited to far below the transonic regime. Therefore w can't be increased beyond an easily achievable value. Meaning thrust T is limited to a (roughly) constant factor times m, mass air flow. Recall mass air flow is pAv. p, air density, we can't change. v is limited to far subsonic, so we can increase thrust T only proportionally to A, the area of the rotor disk. By middle school geometry the area of the disc is pi 2 r. Pi and 2 being constants, the area, and therefore the thrust are directly proportional to r, the radius (the length of the rotor blade),
Quadcopter don't scale. I assume that's what you meant - virtually all of the toy and hobby "drones" are quadcopters.
The power produced by a propeller is proportional to it's length. The weight of a craft, however, is proportional to it's length X width X height.
Suppose we have a toy that's 1 foot X 1 X 1. It's one cubic foot. Perhaps it weighs one pound. The 1 foot prop needs to make 1 pound of thrust.
Now we scale that "ten times bigger". Now the dimensions are 10x10x10. That's 1,000 cubic feet! "Ten times the size" is about a THOUSAND times the weight. But our prop is only ten times as long, so it makes ten times the thrust, enough to lift TEN pounds, not a thousand pounds.
In other words, as the size of craft increases, weight increases with roughly the size (length) CUBED. Prop thrust only increases directly proportional to size (length).
It's therefore therefore relatively easy to lift a small craft with props, but the power requirements go up real fast as the size increases, until you basically hit a wall of impossible physics. The largest helicopters that can be physically built carry about 40 people, whereas an A380 plane seats 853 people.
That is a good argument you can make with your elected representatives. You can write to them about what copyright laws would most effectively promote progress of the Arts and sciences. You can tell them that if they vote for stronger copyright, you'll volunteer as part of their opponent's campaign.
It is not the province of the courts to decide which laws are effective, but how they should be worried in order to be most effective. The court, made up of judges appointed for life who will never answer to voters, has ruled that its own power is limited to the question of if Congress could think that the laws they wrote might further the objectives listed in the Constitution.
You may say you (and a thousand like-minded individuals) have little influence with a Congressman who will soon be up for re-election. To whatever extent that's true, you have even less influence with a federal judge appointed for life, so we probably don't want federal judges deciding which laws are best and most effective, only intervening if the Congressman (who will be facing re-election next year) CLEARLY passed a law with no possible connection to the purposes allowed by the Constitution.
One thing you are allowed to do is particularly relevant to research. You can write an article or make a video about the research and its results. You cannot just read the other person's paper out loud. If you're reading their words out loud it's still there words and they have copyright.
They do not have copyright on the facts. Facts are not protected by copyright. So you can read the research paper, then put it aside and then make a video telling us about what you read.
You can allow people do to whatever with your papers. There are several Creative Commons licenses you might use, or the GNU Free Documentation License (GNU FDL).
That applies to YOUR papers. If your employer paid you to sit in their office and use their computer to write something for their use about their research, it may be their paper. Your right would be getting the pay check.
> Am I free to get a copy of these papers, and make a recording of them, and put that recording on YouTube?
Generally no, unless the license / author / copyright holder allows it. If you want to take someone's work and monetize it with YouTube ads, you'll have to talk to them about if they want to get a cut. An audio copy is a copy, and authors control who is allowed to publish copies unless it's fair use.
Fair use can get complex, but basically the idea is that if the new copy competes commercially with the author's authorized copies, it's probably not fair use. Again, if you want to take someone's work and monetize it with YouTube ads, you'll have to talk to them about if they want to get a cut.
You can do certain things that are considered fair, such as quoting a few sentences from someone else's book, in your own book or long-term video. You'd be selling YOUR book, which has it's own value, rather reselling their work without permission. The fact that your work quotes a few lines of theirs wouldn't be the main value offered.
If you don't like the result, you'll need a different argument, because while the Constitution only authorizes the federal government to do about a dozen pecific things, protecting copyright is one of those twelve things:
Article 1 - Section 8, powers of the federal government (clause 8): âoeTo promote the progress of science and useful arts, by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveries.â
You might advocate for a statute saying that any papers which in any way relate to any research which benefitted from any taxpayer funding must be placed in the public domain. The practical effect of that would be debatable and hard to predict, but it would be a cogent proposal. Pretending that the Constitution says the opposite of what it says in Section 8 is not a reasonable argument.
> I get this and I get how in certain localized examples it might be the case. However, I don't really see how this can be the case on a national scale
Nationally, almost two-thirds of the population lives in only 3.5% of the land area, according to one government publication. Another set of census data has 80% of Americans living in "urban areas", which total 3% of the land.
So it's very easy for the percentage of people covered to be very different from the percentage of land area covered.
This fact makes all kinds of infrastructure in the US very different than other countries. We have vast areas, millions of square miles, with very few people. France has 1,717 people per square mile, the US has 85. With 25 times as many people in a given area, communication, transportation methods and other infrastructure that makes sense in France or other European countries doesn't work at all in the US, which has 96% less people per area.
> If Verizon's customer base were so skewed in that way, they would be spending very large amounts of money to serve a very small customer population across a very large area.
Just the other day we had a couple stories about a carrier sending notices to something like 0.3% of their customers, who live out in the boonies and are roaming on towers owned by another carrier, but they are streaming TV shows.
Consider some Texas counties. Harris county (Houston) and Dallas county each have millions of people. Loving county has 100 people. They are roughly the same size in terms of geographic area.
Suppose Verizon covers Dallas county and Loving county. T-Mobile covers Dallas county, but not Loving. T-Mobile would then cover roughly HALF the geographic area that Verizon does, while covering 99.996% of the people.
You've heard the expression "in theory, theory and practice are the same. In practice, they are not."
Theoretical calculation can show why something is IMPOSSIBLE. It cannot show that there is no unforeseen, insurmountable impediment. Only actually doing it can prove that there is not anything that makes it impossible to actually do.
Having said that, accomplishing each part, separately, is strong evidence that the entire process can be done. If people build appropriately sized canals in similar geography using only tools and technologies available to the ancient Egyptians, and they can (separately) build appropriate barges, and another group can move the blocks to where the barges would have been, it's reasonable to think they probably could have combined each of these steps.
Exactly. (Note my original subject line, "consumers left the desktop".)
> As I see it, it's desktop-vs-pocket, not Windows vs Android
Yes, Windows is popular on the desktop like Wichita brand is the most popular buggy whip.
What I didn't say in my earlier post is that consumers did NOT move from Windows desktops to Windows Phone. They left the desktop AND Windows behind, replacing them with phones/tablets and Android.
There is a lot of truth to that. The article mentions business desktop and consumer desktop.
Microsoft is still very popular on business desktops, of course. Windows on the desktop is NOT popular with consumers. Consumers have largely left the Windows desktop, moving to Android. Even if you leave out iPhone, people bought more Android devices last year than the total sales of Windows devices by both business and consumers combined. For consumers, Android and the mobile form factor are three to four times more popular than the Windows desktop.
Of course, with the UI on Android, some of the storage and processing is being done on the server - by Linux. What consumers use is a Linux-based product which communicates to other Linux-based systems.
While saying "Windows is most popular on the desktop" is technically true, it's a lot like saying "David Duke is popular with the KKK". True, but that doesn't mean that either Windows or David Duke are well-liked.
> more rapid degradation of the operating system as it tries harder to cater to everybody.
That would have been a reasonable prediction 30 years ago. For the last couple decades, almost all supercomputers have used Linux, as have many embedded systems, most web servers, and now most phones / mobile devices use Linux, each with an appropriate UI on top. The fact is, Linux does suit a vast array of very different use cases, and that has worked out very well.
One reason that has worked well is new use cases, such as mobile and cloud. When there was suddenly a need for an operating system well-suited to run the hardware cloud hosts, Amazon and others choose the OS that had already been proven to be quite flexible, and made it even more flexible as they extended it's usefulness in that role. When the Android team needed as OS (not GUI shell) well-suited for advanced mobile devices, they chose Linux because it had been proven to be flexible. They made it even more flexible. So it's a cycle. The more different uses Linux is put to, the more flexible and modular it becomes, making it well suited to applications that don't even exist yet.
> For the next sprint, you use as likelely doable number the actual completed SP from thr current/just finished sprint.
We're partially in agreement. I said project management should see this team does about 98 points per sprint.
The team likely does some points that aren't their current main project - a few points supporting last month's project, for example. Some companies include points for things like annual compliance training, which is not part of this project. So we can expect that some of what gets done will not be part of this project.
Also, there is how much will LIKELY be done and how much they can PROMISE. If you're telling your biggest customer, or even top brass at your own large company, when the project will be done, you should give a conservative estimate, thinking "we can do at least 85 points. Probably around 97, but at least 85, so let's assume 85 in the plan we present to the board." It's far better to complete a project ahead of schedule than to behind schedule.
Indeed, while poorly done planning is useless, or worse, PROPER planning can be VERY useful.
Here's a very important fact - programmers consistently over-estimate how much they can get done in a week or a month. Consistently, that's the key word. We're wrong about how long things will take, but we're wrong in a fairly predictable way. If tasks are well defined, programmers are pretty good at estimating the RELATIVE size of job - task A will likely take about twice as long as task B. Here's what the planned productivity vs actual completed tasks might look like for a typical Agile team, with the amount done measured in "story points":
The team fell short of their plan every time. And they pretty consistently get about 98 points. If management believes the 131 number, there will be problems. It works pretty well if management looks at historical fact and says "this team completes about 98 points per sprint. Let's do the project plan based on 85 points total for the team."
Let's address the "delusions" (straw men) that the author sets up:
> The plan is perfect and guarantees success;
Perfection is not required for something to be valuable. The author's proposal is even LESS perfect. While a plan can't guarantee success, it does at least define success, so you know when you're done, and what you're aiming for. Failing to plan, on the other hand, almost guarantees perpetual scope-creep, where a project can never be a success because it never ends.
> The cost of forming and dissolving teams is zero;
Very often the cost of forming a team is WORTH IT
> The cost of functional silo hand-offs is zero;
Again, not zero, but worth it
> The bigger and more comprehensive the plan, the better;
If you don't have a big-picture plan of what your company or organization is trying to do, what are the odds that you'll accidentally accomplish it?
More specifically, what often happens without a big-picture plan is that functional level teams such as programmers do cool stuff that gets abandoned shortly afterward. They may spend a month integrating the systems of a division that gets sold off two months later. They may do cool stuff for managing desktop applications, while another team is busily moving everything to the cloud.
> Predictability and efficiency are paramount.
Your idea for what you want your team to do sounds good. My different idea sounds good. So does Kevin's idea. Unless we find a way to predict how long these projects will take, WE DON'T KNOW IF WE SHOULD DO THEM AT ALL. There are many, many projects that should be done if we can do them this week, and should not be done if it'll take a year. Yes, predictability *is* important. At a much higher level, the executives at your young, growing company are borrowing millions of dollars to fund the company until it becomes profitable. Those loans start coming due in three years. Yes, for a young company, it's very survival depends on predicting how long these will take and how much they will cost. Predicting is hard (though certain methods make it much easier), but it's essential.
We don't know how much Microsoft was paying to send the traffic to Bing, and how much they offered to keep the Siri-Bing deal.
It may be that Microsoft offered $4 billion, but Apple decided to use Google for its better results, foregoing the additional $1 billion that Microsoft offered.
> I think most librarians and bibliophiles would find that suggestion offensive.
I've suggested that library funds ought NOT be used entirely to push a particular political agenda, that perhaps a library should buy an unabridged dictionary before it buys dozens of "transgender children" books. I'm sure that idea, that basic English is more important than their political ideology, offends some people, but I don't think MOST.
I also suggested that basic science books may, in some cases, be more important than having even more copies of each of Trump's books.
> Literature from opposing viewpoints is important.
Opposing what? 100% of Library Association leadership who donated in 2016 donated to Democrats only. ALA leaders think opposing Trump is important, important enough to spend their own money on. Assuming they are human, their biases will affect their ideas of which advocacy works are good and should be purchased for the library. They'd not be human if they weren't affected by their own bias.
Personally, I think that when presenting one side of a contentious issue, the other side should also be presented as well - "some people think this, other people think that". Even more important for a school or public library, I think, is the basic, non-contentious science, math etc which can be used to evaluate ALL arguments. I would start with reference works such as dictionaries, almanacs, an atlas etc, before getting into opinion pieces or advocacy works which should reference those reference works. For example, a reader can't make an informed evaluation of how a tax cut or tax increase may affect the federal budget unless they first know what mandatory spending and discretionary spending are. The school or library should have material for people to find out what the federal budget currently is, and how it's created and analyzed, before buying more stuff advocating what someone thinks the budget should be.
To be informed a issues relating to "transgender children", rather than merely progandized, it would be of great help to have books for people to learn about what chromosomes are, what hormones are and how they affect our bodies, etc.
In other words, I think government, both government schools and government-funded libraries, should seek FIRST to inform, before they advocate. Someone who has read about chemistry and other sciences can make up their mind about acid rain, presenting a lot of stuff about acid rain while refusing to stock chemistry books is propagandizing people, not educating them.
Additionally, advocacy groups already do a pretty good job of getting their message out. The tax payer doesn't need to be assisting the NRA and the MoveOn as much as we need to be helping people get informed on the objective facts, in my opinion. So when we're at the bottom of the list, we can afford one more book, I'd prefer a fact-based book about actual historic events over anything put out by either MoveOn or the NRA. The advocates can fight it out on CNN and Fox, in my opinion.
> In conclusion, I agree on the part that no one should have the right to force or forbid on kids reading books. The decision should be on their parents. Thus, some books should be banned from public schools but no book should be banned from public libraries.
I agree, in general. Adults can generally decide for themselves what they want to do, including what they want to read. That's entirely different from what they force all children to do and to read.
I also know the public library, which we all pay for, has a certain budget and a certain amount of space, so they can get X number of new books each year. Though we're all paying for the books, only one or two or perhaps three people choose the books we buy for our public library. I'm sure that group time to time the person choosing the books picks mostly books pushing their favored political idealogy and world-view. That should be resisted.
You can certainly imagine someone saying "wait a minute, our library can't afford an unabridged dictionary, but can afford four copies of each of Trump's 19 books? Or no new science books, but a dozen new books about transgender children? One might reasonably challenge some of the Trump books, or the transgender kids books, as being less essential / less appropriate than other options that would otherwise be purchased with that money. That's a fundamental difficulty in American politics and culture - about half the population says "this sounds good, so we should do it", forgetting that means spending our resources there INSTEAD OF somewhere else. About half of us just don't "get it" that resources or limited, no matter what the topic, so the argument isn't "this might be okay, we should do it", we need to be able to say "this is the very best possible use of available resources, so we should do this rather than spending the money on anything else."
The summary says most of the challenges are NOT about public libraries, but about school curriculum. One example being ELEMENTARY school having kids read about a transgender child.
So yes, "appropriate for age group" is a very valid concern - there are certainly books that are available to adults, but we shouldn't force all third and fourth graders to read them.
Multiple books on the list were about transgender children, presenting that as normal. It could well be argued that parents shouldn't be putting their children through multiple surgeries and heavy doses of unnatural hormones to turn a boy into a girl or vice versa, in the vast majority of cases. That's the kind of thing a person ought to decide for themselves, making an informed decision when they are an adult, some would say.
One might reasonably think that having surgeries done on your little boy to turn him into a little girl may, in many cases, be child abuse, so forcing elementary school kids to read that is normal may not be appropriate.
I don't care to argue for or against on any of these issues, but they are certainly issues on which reasonable people may disagree. On such issues, perhaps the government schools shouldn't be forcing this stuff on grade-school kids. If you want to teach your kids that it's normal to chop off a little boys penis, you can do that, but I don't see that you have a need or a right to force that on every other family.
> will give you a more stable product more quickly.
Weakly typed will more quickly produce less robust software, which is perfect for one-time use scripts, small programs written for well-known, well-defined inputs, etc.
As an example, suppose I have a log file of the format:
URL - bytes - epoch - username
If I want to produce some summary statistics from that particular log file, to use in my year-end presentation, a weakly typed language will let me whip up a simple script very quickly.
On the other hand, if I'm deploying production software to the web, where it will encounter unknown user input in different character sets thousands of times per day, I'd want to take a few more minutes of development time to have more robust software. That's when strong typing is good.
Sometimes "quick and dirty" is what you want, sometimes "careful and reliable" is what you want. Duct tape is famous for a reason, and high strength bolts are used for a reason. Each has their place.
The claim was: > Short term profit is the most important goal.
That's obviously very false. Yes, they did figure they eventually make a profit MANY YEARS LATER. Not this quarter, not next quarter, not next year. So very much the opposite of "short term profit". Rather, they made long term investment.
> it is disingenuous to say people running facebook did not focus on profits for years.
The fact is, they didn't even discuss how they would eventually make revenue for many years. Their FOCUS was on getting more users. Sure they wanted to make money some day, but they didn't do that by focusing on profit; they did that by focusing on users. They figured, correctly, that once they had a hundred million happy users they could figure out profit then - years later. So they focused on the user base, paying no mind to revenue or profit. It worked.
YouTube did the same. That's the correct strategy for a rapidly growing new market - spend the first several years getting bigger, while losing tons of money. Focusing on short-term profit in a rapidly growing new market is how you make $100,000 before shutting down, losing out to the companies who are focused on long term growth and unconcerned with near-term profit.
Yet, companies like Facebook, Amazon, etc spend 10 years or more losing money in the expectation that it'll pay off 10 years later. Amazon was founded in 1994 and continued to invest for the future (lose money) until 2013, when it was time to turn a small profit.
Five years after launching Facebook, in 2008, Zuckerberg was asked about plans to make a profit with Facebook one day. He said "in three years or so it'll be time to start thinking about how to monetize it."
YouTube was launched by PayPal employees in 2005 and focused on investing (losing money) in order to get more viewers until 2010, five years.
The actual fact is that Zuckerberg ran Facebook for many years without even thinking about how they'd EVENTUALLY make money long-term, much less focusing on *short-term* profit. Heck, it wasn't until after they'd been running Facebook for 5 years, and had millions of users, that they decided the way they would eventually make profit was by running advertising. Profit simply wasn't something these companies focused on at all.
The power of modern comes from nitroglycerin, the same explosive used in Dynamite. It's a "high explosive", meaning it detonates, explodes all by itself.
Black powder, on the other hand, merely burns quickly. Black powder is very finely powdered charcoal very thoroughly mixed with oxygen-rich saltpetre. The oxygen in the saltpetre helps the charcoal burn faster. Charcoal is hard to light, so a little sulfur is added to make it easier to light. (The hard part is grinding them into a fine enough powder and mixing them so thoroughly that practically every molecule of charcoal is touching a molecule of saltpetre, and doing this grinding and mixing without setting it off.)
A pile of black powder won't explode. When black powder gets interesting is when it's burned inside a closed container. The resulting fumes increase pressure in the container, until the container bursts open (or the pressure sends a musket ball down the barrel).
So you're basically right, you just got the two switched.
Something that explodes by itself (detonates) is called a high explosive. Modern powder contains high explosive. Something that just burns fast, possibly causing it's container to burst, is called a low explosive.
I've made a lot of black powder. It's fun. I made a few MILLIGRAMS of high explosive once. I won't do that again. High explosives are not to be played with.
Slashdot Mirror
Yes, of course you're right. It's the AREA of the disk, multiplied by the velocity, which determines how much air is moved at what rate, which equals how much thrust is created (Newton's third law). I typed it as circumference rather than area.
What I didn't go into was a consideration with real props which brings it closer to directly proportional, so the actual real-life performance is in between the area and the circumference. The inner part of the blade is of course moving slower than the tips, in terms of linear speed. In other words, if the rotor tips are moving through the air at 400MPH, halfway toward the hub it's only slicing through the air at 200MPH. So the portion of the rotor which is delivering maximum power is at the ends, measured by the circumference.
Does that make sense? The total area is proportional to r^2, but the area of blade working at full speed is proportional to just r. Meaning the total thrust is between X * r and X * r^2.
Your correction points out why large rotorcraft normally use one lifting rotor rather than multiple as hobby craft often do. A single 40 foot rotor has twice the swept area of the two 20-foot rotors which would fit on the same airframe. Of course, when you need rotor too big to build and affix to the airframe, such as a heavy-lift copter, you may end up with tandem rotors simply because a 120' rotor is Impractical.
There are similarities and differences. Before the EU was formed, each of the 28 countries already had their own approval process. After the formation of the EU, which is principally an economic and trade alliance, a drug approved in ANY EU country could be sold in ALL EU countries. Therefore a pharmaceutical company could choose which of the 28 countries would likely approve the drug most easily / quickly / cheaply. Commonly, a pharmaceutical company will apply in two or three countries at once and see which one approves it first.
Some drugs are now required to go through one of several centralized EU approval processes instead - and there are four for them to choose from. Being run by the EU, the heritage of these agencies is based on promoting commerce between EU countries - the EU is not focused on consumer protection and safety.
In the US, a maker has to get approval from the FDA. They don't get to choose different agencies to seek approval from.
The DA started as a consumer protection agency, trying to make sure drugs were safe. Later, they got mandate to make sure they are effective. The FDA doesn't have the heritage of coming from an organization trying to promote commerce, like the EU does.
Therefore historically it's been easier and cheaper to get drugs approved in Europe than in the US. Europeans got cheaper medicines faster, Americans got better, more expensive medicine. (The difficult and expensive FDA process isn't a total waste).
In the last few years, there has been pressure on both sides of the Atlantic to be more like the other guys. Americans want cheaper drugs, sooner. Europeans want want better, safer drugs. I guess the grass is always greener on the other side of the fence. So each process has become more like the other and the difference isn't as extreme as it once was.
For an actuator disk of area A, with induced velocity v at the rotor disk, and with p as the density of air, the mass flow rate m through the disk area is:
m =pAv
By conservation of mass, the mass flow rate is constant across the slipstream both upstream and downstream of the disk (regardless of velocity). Since the flow far upstream of a helicopter in a level hover is at rest, the starting velocity, momentum, and energy are zero. If the homogeneous slipstream far downstream of the disk has velocity w, by conservation of momentum the total thrust T developed over the disk is equal to the rate of change of momentum, which given zero starting velocity is:
T=mw
Because tip velocity can't exceed c, w is limited to far below the transonic regime. Therefore w can't be increased beyond an easily achievable value. Meaning thrust T is limited to a (roughly) constant factor times m, mass air flow. Recall mass air flow is pAv. p, air density, we can't change. v is limited to far subsonic, so we can increase thrust T only proportionally to A, the area of the rotor disk. By middle school geometry the area of the disc is pi 2 r. Pi and 2 being constants, the area, and therefore the thrust are directly proportional to r, the radius (the length of the rotor blade),
Quadcopter don't scale. I assume that's what you meant - virtually all of the toy and hobby "drones" are quadcopters.
The power produced by a propeller is proportional to it's length.
The weight of a craft, however, is proportional to it's length X width X height.
Suppose we have a toy that's 1 foot X 1 X 1. It's one cubic foot. Perhaps it weighs one pound. The 1 foot prop needs to make 1 pound of thrust.
Now we scale that "ten times bigger". Now the dimensions are 10x10x10. That's 1,000 cubic feet! "Ten times the size" is about a THOUSAND times the weight. But our prop is only ten times as long, so it makes ten times the thrust, enough to lift TEN pounds, not a thousand pounds.
In other words, as the size of craft increases, weight increases with roughly the size (length) CUBED. Prop thrust only increases directly proportional to size (length).
It's therefore therefore relatively easy to lift a small craft with props, but the power requirements go up real fast as the size increases, until you basically hit a wall of impossible physics. The largest helicopters that can be physically built carry about 40 people, whereas an A380 plane seats 853 people.
That is a good argument you can make with your elected representatives. You can write to them about what copyright laws would most effectively promote progress of the Arts and sciences. You can tell them that if they vote for stronger copyright, you'll volunteer as part of their opponent's campaign.
It is not the province of the courts to decide which laws are effective, but how they should be worried in order to be most effective. The court, made up of judges appointed for life who will never answer to voters, has ruled that its own power is limited to the question of if Congress could think that the laws they wrote might further the objectives listed in the Constitution.
You may say you (and a thousand like-minded individuals) have little influence with a Congressman who will soon be up for re-election. To whatever extent that's true, you have even less influence with a federal judge appointed for life, so we probably don't want federal judges deciding which laws are best and most effective, only intervening if the Congressman (who will be facing re-election next year) CLEARLY passed a law with no possible connection to the purposes allowed by the Constitution.
One thing you are allowed to do is particularly relevant to research. You can write an article or make a video about the research and its results. You cannot just read the other person's paper out loud. If you're reading their words out loud it's still there words and they have copyright.
They do not have copyright on the facts. Facts are not protected by copyright. So you can read the research paper, then put it aside and then make a video telling us about what you read.
> I won't object if you do that with my papers.
You can allow people do to whatever with your papers. There are several Creative Commons licenses you might use, or the GNU Free Documentation License (GNU FDL).
That applies to YOUR papers. If your employer paid you to sit in their office and use their computer to write something for their use about their research, it may be their paper. Your right would be getting the pay check.
> Am I free to get a copy of these papers, and make a recording of them, and put that recording on YouTube?
Generally no, unless the license / author / copyright holder allows it. If you want to take someone's work and monetize it with YouTube ads, you'll have to talk to them about if they want to get a cut. An audio copy is a copy, and authors control who is allowed to publish copies unless it's fair use.
Fair use can get complex, but basically the idea is that if the new copy competes commercially with the author's authorized copies, it's probably not fair use. Again, if you want to take someone's work and monetize it with YouTube ads, you'll have to talk to them about if they want to get a cut.
You can do certain things that are considered fair, such as quoting a few sentences from someone else's book, in your own book or long-term video. You'd be selling YOUR book, which has it's own value, rather reselling their work without permission. The fact that your work quotes a few lines of theirs wouldn't be the main value offered.
If you don't like the result, you'll need a different argument, because while the Constitution only authorizes the federal government to do about a dozen pecific things, protecting copyright is one of those twelve things:
Article 1 - Section 8, powers of the federal government (clause 8):
âoeTo promote the progress of science and useful arts, by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveries.â
You might advocate for a statute saying that any papers which in any way relate to any research which benefitted from any taxpayer funding must be placed in the public domain. The practical effect of that would be debatable and hard to predict, but it would be a cogent proposal. Pretending that the Constitution says the opposite of what it says in Section 8 is not a reasonable argument.
> I get this and I get how in certain localized examples it might be the case. However, I don't really see how this can be the case on a national scale
Nationally, almost two-thirds of the population lives in only 3.5% of the land area, according to one government publication. Another set of census data has 80% of Americans living in "urban areas", which total 3% of the land.
So it's very easy for the percentage of people covered to be very different from the percentage of land area covered.
This fact makes all kinds of infrastructure in the US very different than other countries. We have vast areas, millions of square miles, with very few people. France has 1,717 people per square mile, the US has 85. With 25 times as many people in a given area, communication, transportation methods and other infrastructure that makes sense in France or other European countries doesn't work at all in the US, which has 96% less people per area.
> If Verizon's customer base were so skewed in that way, they would be spending very large amounts of money to serve a very small customer population across a very large area.
Just the other day we had a couple stories about a carrier sending notices to something like 0.3% of their customers, who live out in the boonies and are roaming on towers owned by another carrier, but they are streaming TV shows.
Consider some Texas counties. Harris county (Houston) and Dallas county each have millions of people. Loving county has 100 people. They are roughly the same size in terms of geographic area.
Suppose Verizon covers Dallas county and Loving county. T-Mobile covers Dallas county, but not Loving. T-Mobile would then cover roughly HALF the geographic area that Verizon does, while covering 99.996% of the people.
Had you just posted the links, you'd have secured the moral high ground and made GP look like a fool and a jerk.
By packaging your reply in sarcasm, you gave up the high ground.
You've heard the expression "in theory, theory and practice are the same. In practice, they are not."
Theoretical calculation can show why something is IMPOSSIBLE. It cannot show that there is no unforeseen, insurmountable impediment. Only actually doing it can prove that there is not anything that makes it impossible to actually do.
Having said that, accomplishing each part, separately, is strong evidence that the entire process can be done. If people build appropriately sized canals in similar geography using only tools and technologies available to the ancient Egyptians, and they can (separately) build appropriate barges, and another group can move the blocks to where the barges would have been, it's reasonable to think they probably could have combined each of these steps.
> Consumer have largely left the desktop, period.
Exactly. (Note my original subject line, "consumers left the desktop".)
> As I see it, it's desktop-vs-pocket, not Windows vs Android
Yes, Windows is popular on the desktop like Wichita brand is the most popular buggy whip.
What I didn't say in my earlier post is that consumers did NOT move from Windows desktops to Windows Phone. They left the desktop AND Windows behind, replacing them with phones/tablets and Android.
There is a lot of truth to that. The article mentions business desktop and consumer desktop.
Microsoft is still very popular on business desktops, of course. Windows on the desktop is NOT popular with consumers. Consumers have largely left the Windows desktop, moving to Android. Even if you leave out iPhone, people bought more Android devices last year than the total sales of Windows devices by both business and consumers combined. For consumers, Android and the mobile form factor are three to four times more popular than the Windows desktop.
Of course, with the UI on Android, some of the storage and processing is being done on the server - by Linux. What consumers use is a Linux-based product which communicates to other Linux-based systems.
While saying "Windows is most popular on the desktop" is technically true, it's a lot like saying "David Duke is popular with the KKK". True, but that doesn't mean that either Windows or David Duke are well-liked.
> more rapid degradation of the operating system as it tries harder to cater to everybody.
That would have been a reasonable prediction 30 years ago. For the last couple decades, almost all supercomputers have used Linux, as have many embedded systems, most web servers, and now most phones / mobile devices use Linux, each with an appropriate UI on top. The fact is, Linux does suit a vast array of very different use cases, and that has worked out very well.
One reason that has worked well is new use cases, such as mobile and cloud. When there was suddenly a need for an operating system well-suited to run the hardware cloud hosts, Amazon and others choose the OS that had already been proven to be quite flexible, and made it even more flexible as they extended it's usefulness in that role. When the Android team needed as OS (not GUI shell) well-suited for advanced mobile devices, they chose Linux because it had been proven to be flexible. They made it even more flexible. So it's a cycle. The more different uses Linux is put to, the more flexible and modular it becomes, making it well suited to applications that don't even exist yet.
> For the next sprint, you use as likelely doable number the actual completed SP from thr current/just finished sprint.
We're partially in agreement. I said project management should see this team does about 98 points per sprint.
The team likely does some points that aren't their current main project - a few points supporting last month's project, for example. Some companies include points for things like annual compliance training, which is not part of this project. So we can expect that some of what gets done will not be part of this project.
Also, there is how much will LIKELY be done and how much they can PROMISE. If you're telling your biggest customer, or even top brass at your own large company, when the project will be done, you should give a conservative estimate, thinking "we can do at least 85 points. Probably around 97, but at least 85, so let's assume 85 in the plan we present to the board." It's far better to complete a project ahead of schedule than to behind schedule.
Indeed, while poorly done planning is useless, or worse, PROPER planning can be VERY useful.
Here's a very important fact - programmers consistently over-estimate how much they can get done in a week or a month. Consistently, that's the key word. We're wrong about how long things will take, but we're wrong in a fairly predictable way. If tasks are well defined, programmers are pretty good at estimating the RELATIVE size of job - task A will likely take about twice as long as task B. Here's what the planned productivity vs actual completed tasks might look like for a typical Agile team, with the amount done measured in "story points":
Sprint #. Plan Actual completed
Sprint 1. 124 98
Sprint 2. 105 96
Sprint 3. 131 102
Sprint 4. 116 97
The team fell short of their plan every time. And they pretty consistently get about 98 points. If management believes the 131 number, there will be problems. It works pretty well if management looks at historical fact and says "this team completes about 98 points per sprint. Let's do the project plan based on 85 points total for the team."
Let's address the "delusions" (straw men) that the author sets up:
> The plan is perfect and guarantees success;
Perfection is not required for something to be valuable. The author's proposal is even LESS perfect. While a plan can't guarantee success, it does at least define success, so you know when you're done, and what you're aiming for. Failing to plan, on the other hand, almost guarantees perpetual scope-creep, where a project can never be a success because it never ends.
> The cost of forming and dissolving teams is zero;
Very often the cost of forming a team is WORTH IT
> The cost of functional silo hand-offs is zero;
Again, not zero, but worth it
> The bigger and more comprehensive the plan, the better;
If you don't have a big-picture plan of what your company or organization is trying to do, what are the odds that you'll accidentally accomplish it?
More specifically, what often happens without a big-picture plan is that functional level teams such as programmers do cool stuff that gets abandoned shortly afterward. They may spend a month integrating the systems of a division that gets sold off two months later. They may do cool stuff for managing desktop applications, while another team is busily moving everything to the cloud.
> Predictability and efficiency are paramount.
Your idea for what you want your team to do sounds good. My different idea sounds good. So does Kevin's idea. Unless we find a way to predict how long these projects will take, WE DON'T KNOW IF WE SHOULD DO THEM AT ALL. There are many, many projects that should be done if we can do them this week, and should not be done if it'll take a year. Yes, predictability *is* important. At a much higher level, the executives at your young, growing company are borrowing millions of dollars to fund the company until it becomes profitable. Those loans start coming due in three years. Yes, for a young company, it's very survival depends on predicting how long these will take and how much they will cost. Predicting is hard (though certain methods make it much easier), but it's essential.
We don't know how much Microsoft was paying to send the traffic to Bing, and how much they offered to keep the Siri-Bing deal.
It may be that Microsoft offered $4 billion, but Apple decided to use Google for its better results, foregoing the additional $1 billion that Microsoft offered.
> I think most librarians and bibliophiles would find that suggestion offensive.
I've suggested that library funds ought NOT be used entirely to push a particular political agenda, that perhaps a library should buy an unabridged dictionary before it buys dozens of "transgender children" books. I'm sure that idea, that basic English is more important than their political ideology, offends some people, but I don't think MOST.
I also suggested that basic science books may, in some cases, be more important than having even more copies of each of Trump's books.
> Literature from opposing viewpoints is important.
Opposing what? 100% of Library Association leadership who donated in 2016 donated to Democrats only. ALA leaders think opposing Trump is important, important enough to spend their own money on. Assuming they are human, their biases will affect their ideas of which advocacy works are good and should be purchased for the library. They'd not be human if they weren't affected by their own bias.
Personally, I think that when presenting one side of a contentious issue, the other side should also be presented as well - "some people think this, other people think that". Even more important for a school or public library, I think, is the basic, non-contentious science, math etc which can be used to evaluate ALL arguments. I would start with reference works such as dictionaries, almanacs, an atlas etc, before getting into opinion pieces or advocacy works which should reference those reference works. For example, a reader can't make an informed evaluation of how a tax cut or tax increase may affect the federal budget unless they first know what mandatory spending and discretionary spending are. The school or library should have material for people to find out what the federal budget currently is, and how it's created and analyzed, before buying more stuff advocating what someone thinks the budget should be.
To be informed a issues relating to "transgender children", rather than merely progandized, it would be of great help to have books for people to learn about what chromosomes are, what hormones are and how they affect our bodies, etc.
In other words, I think government, both government schools and government-funded libraries, should seek FIRST to inform, before they advocate. Someone who has read about chemistry and other sciences can make up their mind about acid rain, presenting a lot of stuff about acid rain while refusing to stock chemistry books is propagandizing people, not educating them.
Additionally, advocacy groups already do a pretty good job of getting their message out. The tax payer doesn't need to be assisting the NRA and the MoveOn as much as we need to be helping people get informed on the objective facts, in my opinion. So when we're at the bottom of the list, we can afford one more book, I'd prefer a fact-based book about actual historic events over anything put out by either MoveOn or the NRA. The advocates can fight it out on CNN and Fox, in my opinion.
> In conclusion, I agree on the part that no one should have the right to force or forbid on kids reading books. The decision should be on their parents. Thus, some books should be banned from public schools but no book should be banned from public libraries.
I agree, in general. Adults can generally decide for themselves what they want to do, including what they want to read. That's entirely different from what they force all children to do and to read.
I also know the public library, which we all pay for, has a certain budget and a certain amount of space, so they can get X number of new books each year. Though we're all paying for the books, only one or two or perhaps three people choose the books we buy for our public library. I'm sure that group time to time the person choosing the books picks mostly books pushing their favored political idealogy and world-view. That should be resisted.
You can certainly imagine someone saying "wait a minute, our library can't afford an unabridged dictionary, but can afford four copies of each of Trump's 19 books? Or no new science books, but a dozen new books about transgender children? One might reasonably challenge some of the Trump books, or the transgender kids books, as being less essential / less appropriate than other options that would otherwise be purchased with that money. That's a fundamental difficulty in American politics and culture - about half the population says "this sounds good, so we should do it", forgetting that means spending our resources there INSTEAD OF somewhere else. About half of us just don't "get it" that resources or limited, no matter what the topic, so the argument isn't "this might be okay, we should do it", we need to be able to say "this is the very best possible use of available resources, so we should do this rather than spending the money on anything else."
The summary says most of the challenges are NOT about public libraries, but about school curriculum. One example being ELEMENTARY school having kids read about a transgender child.
So yes, "appropriate for age group" is a very valid concern - there are certainly books that are available to adults, but we shouldn't force all third and fourth graders to read them.
Multiple books on the list were about transgender children, presenting that as normal. It could well be argued that parents shouldn't be putting their children through multiple surgeries and heavy doses of unnatural hormones to turn a boy into a girl or vice versa, in the vast majority of cases. That's the kind of thing a person ought to decide for themselves, making an informed decision when they are an adult, some would say.
One might reasonably think that having surgeries done on your little boy to turn him into a little girl may, in many cases, be child abuse, so forcing elementary school kids to read that is normal may not be appropriate.
I don't care to argue for or against on any of these issues, but they are certainly issues on which reasonable people may disagree. On such issues, perhaps the government schools shouldn't be forcing this stuff on grade-school kids. If you want to teach your kids that it's normal to chop off a little boys penis, you can do that, but I don't see that you have a need or a right to force that on every other family.
> will give you a more stable product more quickly.
Weakly typed will more quickly produce less robust software, which is perfect for one-time use scripts, small programs written for well-known, well-defined inputs, etc.
As an example, suppose I have a log file of the format:
URL - bytes - epoch - username
If I want to produce some summary statistics from that particular log file, to use in my year-end presentation, a weakly typed language will let me whip up a simple script very quickly.
On the other hand, if I'm deploying production software to the web, where it will encounter unknown user input in different character sets thousands of times per day, I'd want to take a few more minutes of development time to have more robust software. That's when strong typing is good.
Sometimes "quick and dirty" is what you want, sometimes "careful and reliable" is what you want. Duct tape is famous for a reason, and high strength bolts are used for a reason. Each has their place.
The claim was:
> Short term profit is the most important goal.
That's obviously very false. Yes, they did figure they eventually make a profit MANY YEARS LATER. Not this quarter, not next quarter, not next year. So very much the opposite of "short term profit". Rather, they made long term investment.
> it is disingenuous to say people running facebook did not focus on profits for years.
The fact is, they didn't even discuss how they would eventually make revenue for many years. Their FOCUS was on getting more users. Sure they wanted to make money some day, but they didn't do that by focusing on profit; they did that by focusing on users. They figured, correctly, that once they had a hundred million happy users they could figure out profit then - years later. So they focused on the user base, paying no mind to revenue or profit. It worked.
YouTube did the same. That's the correct strategy for a rapidly growing new market - spend the first several years getting bigger, while losing tons of money. Focusing on short-term profit in a rapidly growing new market is how you make $100,000 before shutting down, losing out to the companies who are focused on long term growth and unconcerned with near-term profit.
> short term profit is the most important goal.
That's fun to say, isn't it.
Yet, companies like Facebook, Amazon, etc spend 10 years or more losing money in the expectation that it'll pay off 10 years later. Amazon was founded in 1994 and continued to invest for the future (lose money) until 2013, when it was time to turn a small profit.
Five years after launching Facebook, in 2008, Zuckerberg was asked about plans to make a profit with Facebook one day. He said "in three years or so it'll be time to start thinking about how to monetize it."
YouTube was launched by PayPal employees in 2005 and focused on investing (losing money) in order to get more viewers until 2010, five years.
The actual fact is that Zuckerberg ran Facebook for many years without even thinking about how they'd EVENTUALLY make money long-term, much less focusing on *short-term* profit. Heck, it wasn't until after they'd been running Facebook for 5 years, and had millions of users, that they decided the way they would eventually make profit was by running advertising. Profit simply wasn't something these companies focused on at all.
The power of modern comes from nitroglycerin, the same explosive used in Dynamite. It's a "high explosive", meaning it detonates, explodes all by itself.
Black powder, on the other hand, merely burns quickly. Black powder is very finely powdered charcoal very thoroughly mixed with oxygen-rich saltpetre. The oxygen in the saltpetre helps the charcoal burn faster. Charcoal is hard to light, so a little sulfur is added to make it easier to light. (The hard part is grinding them into a fine enough powder and mixing them so thoroughly that practically every molecule of charcoal is touching a molecule of saltpetre, and doing this grinding and mixing without setting it off.)
A pile of black powder won't explode. When black powder gets interesting is when it's burned inside a closed container. The resulting fumes increase pressure in the container, until the container bursts open (or the pressure sends a musket ball down the barrel).
So you're basically right, you just got the two switched.
Something that explodes by itself (detonates) is called a high explosive. Modern powder contains high explosive. Something that just burns fast, possibly causing it's container to burst, is called a low explosive.
I've made a lot of black powder. It's fun. I made a few MILLIGRAMS of high explosive once. I won't do that again. High explosives are not to be played with.