Google adds a Bitcoin calculator to its search engine solar probe is meant to help scientists prevent satellite outages and reduce risks to airline passengers. A March 23 memo to employees accepts blame and supports action. Company says it removed the malicious apps between April and June 2018. The drivers send faked photos of the vomit in an effort to sell their scam and pocket the charge applied to riders’ credit cards.
The device is a half-sized replica of the 1982 Commodore 64. Part of Google’s Cloud Next event in San Francisco. Sign Up for Our Newsletters Sign up now to receive FORTUNE’s best content, special offers, and much more. Fortune may receive compensation for some links to products and services on this website.
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Join Stack Overflow to learn, share knowledge, and build your career. M9 1a8 8 0 1 0 0 16A8 8 0 0 0 9 1zM8 15. I am trying to build a web application in ASP. NET MVC and need build a pretty complex search feature. When a user enters a search term I want to search a variety of data sources which include documents, tables in the database, webpage urls and some APIs like facebook. Any tips, tutorials and hints would be greatly appreciated.
You are stucked with index storage or with searching, or with query analysis? What portion of that are you having difficulty with? If you’re having trouble building a complex search engine, I would start with a simple one first. Build something that searches documents only, because you’ll eventually need that part. Then move on to database searches. Your question suggests that you’re probably not planing to implement the whole feature from scratch, so here are some links that you may find useful.
Google and display the results in a customized way. A more sophisticated approach is to use some . A popular library is for example Lucene. I could be wrong but there seems to be some activity git-wip-us.
Building the actual search index structures and algorithms is no trivial feat. That’s why people use Lucene, Sphinx, Solr, etc. I recomend taking a look at Solr, it gives you the power of Lucene but it’s much easier to use, plus it adds several convenience features like caching, sharding, faceting, etc. Net, it has a sample ASP. NET MVC app that you can use to see how it works and as a base to your project.
Is it still in active development? I wrote a custom search engine for my MVC 4 site. It parses the View directories and reads all the . Not the answer you’re looking for?
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No, not that one that launched the car— that’s the Falcon Heavy. It can carry more than twice as much payload as the Heavy. SpaceX’s vision is to offer rides to the other side of the planet in around 30 minutes. The rocket would take off from somewhere near a city, launch at sub-orbital speed into space, coast for a few tens of minutes, re-enter the atmosphere, fire its rockets and land at the destination city. Essentially, it would be an ICBM for passengers.
Elon Musk has claimed the an Earth-to-Earth BFR ticket should be around the same price as a commercial economy flight ticket, offering a faster, competitive alternative to air travel. This boggled my mind, so I decided to do a whole heap of napkin math to answer the question: How crazy is this? Is it even crazy at all? Is Elon Musk’s advertised price realistic? Is it possible to bring the cost of a ride on an honest-to-god spaceship down to that level? 500,000, and scale it for the different logistics of going to Earth instead.
A Mars trip is a multi-month journey, so in order to offer everyone living quarters, entertainment, amenities, and cargo space to carry equipment for living on Mars, the spaceship tops out at a maximum capacity of around 100 people. But for a 30 minute intercity trip, none of those amenities will be necessary, and that means we can fit a lot more people on board. The Mars journey is much longer, too. So much longer, in fact, that SpaceX will have to launch five more BFRs into low Earth orbit just to fuel up the passenger vehicle before it departs for interplanetary space.
So to go to Mars, those 100 passengers are actually paying for at least 6 complete BFR launches from the surface of the Earth. We don’t need it, so after discarding the cost of the refuel flights themselves, we can expect to pay about half as much for fuel on an intercity trip. After rockets are fully reusable, the non-fuel costs could go way down. Perhaps the biggest factor in ticket price is reusability, or the number of flights the rocket can make. 26 months, at every Hohman transfer window. At this point, we probably can’t simply divide the ticket price by 730 and dust our hands.
Firstly, the ability to fly a rocket 3650 times without major refurbishment hasn’t been proven yet. SpaceX’s latest, most-reusable incarnation of the Falcon 9— the Block 5— is expected to fly only 10 times before overhaul. Few materials can survive this for very long, which means heat shielding burns away or becomes ruined after only a few uses. There is a second reason why we can’t simply divide the price by reusability: Given that the Mars ship is only ever going carry 500 passengers in its entire life, buying a ticket to Mars is essentially like going in on purchasing an interplanetary spaceship with 499 other people: it’s going to be expensive.
To precisely estimate the cost reduction, we’d have to know not just the reusability, but also what fraction of the ticket will go to flight and ground operations, and what fraction goes to vehicle cost. This is another thing for which good figures are scarce, so it is probably best to amortize the vehicle cost and look at what we have left over to work with. 9000 per ticket needs to be spent amortizing the initial vehicle cost— which is not enough to be competitive with air travel. 100 per ticket, the operations costs dominate the price. 200 more than an airline ticket, rather than 20 times more, if we assume that operations costs are about the same.
1200 international ticket, that’s probably OK. So could Elon’s claim about the price of intercity rocket travel be legitimate? Yes, but only if SpaceX adds at least two more zeros to the number of flights a rocket can make. The importance of this question— and the difficulty of answering it positively— can’t be overstated. On average, there are fewer than 1000 air-accident related deaths per year, worldwide. In short, buying a plane ticket effectively carries no risk to your life and limb.
When you step on the plane, you can be virtually certain that you will step off again unharmed. This makes rocketry about 105 times more dangerous than aviation, and it’s clearly unacceptable. So what does SpaceX have to do to make passenger rocket flights acceptably safe? On the face of things, a rocket is basically a giant pressurized tin can full of flammable liquid balancing on top of a giant explosion— so there’s one very obvious way that things can go wrong. If we look more closely, there are millions of moving parts and sensors that keep that explosion at exactly the right amount explodey-ness, and the rocket balanced on top of it at exactly the right angle— so there are a million less-obvious ways that things can go wrong. I took a look at an inventory of rocket failures since 2000 and tried to break them into major categories by cause. This process can go wrong if sensors send the wrong data, or if the computer misinterprets them, or if the software crashes, or if the situation evolves into something that wasn’t tested, among other things.
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3 of the rocket failures in the list above were because of GNC issues. Loss of thrust If for some reason the engines shut down too early or don’t fire with full force, the rocket doesn’t make it to orbit. 3 of the cataloged failures named a loss of thrust in the cause. SpaceX has done a decent job of building redundancy into its designs.
In fact, an early CRS mission suffered a single engine failure, but the primary mission still made it safely to orbit. Musk has stated that the BFR will have two redundant engines for its re-entry burn, so even if one completely fails, another can be started up and the spacecraft safely landed. The above result is probably an underestimate, though, because it assumes that engine failures are independent events. Rockets are almost entirely pipes and tanks and pumps. Valves love to freeze over and get stuck.
Pipe seals can burst or burn through and send searing hot rocket fuel all over the place. Pressure waves or turbulence can build up inside pipes and cause other parts to fail. Fast-moving fluids can cavitate and scour away even the hardest metals. Valves refuse to open for seemingly no good reason. Metal impurities weaken pressure tank walls.
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Rubber O-rings get unexpectedly stiff in cold morning temperatures. In short, the materials of the rocket don’t live up to standards, or behave in surprising ways in the extreme circumstances of being a rocket. CRS-7 failure was due to an internal strut failing far below its design strength, and the Amos-6 launch pad failure was because of an unexpected interaction between supercooled oxygen and carbon fiber. If that separation doesn’t happen correctly, the mission is basically over. If the spacecraft uses pyrotechnic charges to separate, these could simply be duds and fail to ignite. Other things could go wrong, like a latch getting stuck, or the separation happening at the wrong time. Elon has stated that SpaceX never uses pyrotechnic charges for stage separation, since the parts can’t be tested ahead of time on the ground.
What does SpaceX have to contend with? It would certainly not be easy, but it is plausible that these sorts of issues could be uncovered before actual flight by sufficiently diligent engineers. They lurk in the complexities between systems, in the gaps between disciplines, and in the interpersonal relationships of the builders and engineers. SpaceX, as it is pushing further into the unknown, endures those risks perhaps more than any traditional rocket manufacturer. These are all innovations that are necessary to move the industry into the future, and absolutely should be done.
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However, they are the enemy of consumer-level reliability. Many non-passenger flights will have to be made before the BFR could possibly be deemed safe for general transportation. While they are learning lessons from the failures of the past, there are still new lessons waiting to be learned in the territory they are pushing into. The innovation is not going to let up for the development of BFR— in fact, it is likely to increase.
About 4 or 5 zeroes need to be knocked off the probability of failure in order for consumer travel to appear sane, and it’s not immediately clear yet how that could be done. Noise I’ve seen a lot of comments about the worry of sonic booms— this is a problem, but probably less than many people think, as the vehicle pretty much goes straight up and out of the atmosphere. While in transit over continents, there is no way for it to make a sonic boom. What people do tend to underestimate is the just how loud a rocket launch is. The Saturn V and space shuttle launches were both about 205dB— the BFR, which is larger than both, will certainly not be quieter. 205dB, by the way, is over 3 million times louder than a commercial jet flying 100 feet over your head— something I can’t even wrap my head around. Supposedly this level of sound is enough to melt concrete near the launch pad.
To fall under the FAA’s residential aircraft noise limit of 65dB, how far away would the BFR’s launch pad need to be from any development? Sound attenuates with distance for two reasons: One, by the inverse square law, which arises from the fact that its energy is divided over the surface of a sphere of ever-increasing size as the sound travels away from its source. This works out to about -6dB of attenuation with every doubling of distance from the source. The sound, which is a vibration, has to physically shake the air it travels through, which the air resists due to its viscosity.
Over long distances, this resistance converts some of the acoustic energy to heat, and reduces the volume of the sound as it propagates. This gives us the loudness of the rocket if it were a point source and we were 1 meter away from it— for our 205dB rocket, this works out to 194dB of sound pressure. The result is that the launch pad has to be a minimum of 13 miles from anything. And that explains the boat ride in the video at the beginning of this article: The only reasonable place to put a commercial launch pad within reach of a populated area is off the coast. Right off the bat, this limits Earth-to-Earth space travel to cities which are near large bodies of water. Thankfully, this covers a lot of them, but it does pretty thoroughly exclude major cities on the interiors of continents.
It also complicates logistics quite a bit. While SpaceX does have solid experience landing spaceships at sea, this could potentially be hugely difficult and expensive, and could eat into those formerly-appealing ticket prices. Overall, this is a pretty exciting idea. Hopping from continent to continent through space in a matter of minutes seems right out of the future, and it’s tantalizingly close. Safety is a huge unanswered question, though. SpaceX will likely need many flights and design iterations to learn about how rocket parts wear and fail after a large number of flight cycles.
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There is no data about this now, and SpaceX will be the first to learn it. It will certainly take many tries to get things right. Here’s hoping they can figure it out! If a given engine has a 0.
36,500 launches a year under our assumptions, we should expect 0. 0022 of them to be dual engine failures. Bitcoin is like gold, and gold is good for counting wealth, therefore Bitcoin is good for counting wealth. Bitcoin advocates back then would have dismissed Bitcoin’s slide in popularity as proof of its invalidity, though today they’d probably be just as likely to point to its popularity as evidence of its success.
How Bitcoin works You don’t need to know a whole lot about Bitcoin to understand its basic premise: You have an artificially scarce resource, which in this case happens to be very large numbers with a special mathematical property. That property is what makes the numbers rare, and thus computationally time-intensive to find. As time progresses, the property is designed to become more and more stringent, so new Bitcoin numbers become increasingly difficult to create. There are more technical details which ensure the security of the whole system, but they’re not important to this discussion.
What is important is that it is commonly said that this scarcity is what gives Bitcoin its value. And there are some problems with that. People often say Bitcoin is like gold and highlight the fact that, like gold, it’s valuable because it’s scarce, and because other people believe it’s valuable. I’d like to get a small point out of the way: Mere belief isn’t the sole reason for gold’s value. If everyone suddenly stopped caring about how pretty and shiny gold is, it would still have some utility which could be cashed in on.
Gold’s utility beyond a material yardstick of wealth is one thing that lends some credibility to its value. This is not true for Bitcoin. A bitcoin is a number, and that number has no utility outside of its ability to be accepted by someone else. Unlike gold, the the minimum value of a bitcoin is zero— its value if everyone stops believing it works. This is one reason why a bitcoin is a risky way to hold assets.