Could a third of the world's population be on another planet in 100 years?

Question: With the technologies that we have got, is it possible to completely migrate 1/3rd of the world's population to another planet which has characteristics similar to those of earth ? Possibly it will happen.
Comment: 1. Move ten people to the other planet, 2. kill all but twenty people on Earth :)
Comment: As always, Randall Munroe has thought of it: [XKCD Move everyone out to space](https://what-if.xkcd.com/7/)
Comment: If 1/3rd of the world's population lived on another planet... they wouldn't be part of this world's population any more...
Comment: I have to ask, why would all those people *want* to migrate? If it's similar to Earth, what's the benefit? Jobs, survival, or just some sort of adventurous spirit driving them to explore the cosmos?
Comment: I have to ask for clarification on this, are you referring to 1/3 of the *current* population, or 1/3 of the projected population in 100 years?
Comment: Assuming that we will have a nuclear war within the next 100 years, which is not alltogether unlikely, the world population might be quite small, so 1/3 of that won't be a lot of people.
Comment: @Damon So there's a possibility.
Answer: That would be no.  While in 100 years we just might have the ability to travel to another planet (and if you count in solar system then it will be much less) it would still take a HUGE amount of resources to move 2,300,000,000 people off this rock.  That is about 1/3 of the current population.
Lets just take China, it's is 1/8th of the worlds population currently.  Let's say we want to move them all, every single person, to the US.  Just getting them on planes and boats and crossing.
The 747 average about 500 people per flight (18 hrs), super tankers might be able to squeeze in 20,000 (WAG (Wild A$$ Guess) for a 2 week trip across the Pacific).  So say half and half for this little number exercise.  500,000,000 people by plane and the same by ship.  that would take 1,000,000 plane trips and 100,000 ship trips.  Lets say there are about 1,000 of these tankers, it would take each 25 trips, at a month turnaround time for a total of 25 months.  Say 1000 airplanes, are also working, that would be 1000 trips each, at a minimum of 1.5 days turnaround, that's 60 months of constant flying (no time for repairs and maintenance).  So moving 1/3 of the the human population OFF THE PLANET is virtually nil.
Remember this is just transporting them from one side of the ocean to the other, with a couple suitcases and enough food for a very short trip.  The cost of putting people into orbit is significantly more, and having a living environment out there the cost goes up.  Another WAG if we have 100,000 humans living off Earth in 100 years I think we're going to be doing pretty good.
EDT Notes:
Some Math errors were pointed out and (I found some more!) A couple by a factor of 10.  I also bumped up the tankers passenger list from 5000 to 20,000 (might still be low) but don't want diseases to spread among those traveling and it isn't like those still waiting are going to die if they don't leave in time.
Any other mistakes I missed (or added?)
Comment: I'm not seeing the logic here. It takes 1/200th of a 100 years to move that many people around on Earth and therefore it's not possible? It takes six months to do it on Earth, therefore 100 years isn't enough for another planet?
Comment: So the answer will be a BIG ZERO...But i think there will be a breakthrough technology which could make it a reality.Keep our hopes.
Comment: @Samuel It takes 10 months to to move a 1,000,000,000 people 11,000 miles.  reusing the same equipment over and over.  Shipping is very cheap, planes a bit more expensive.  It costs a fortune to send 1 astronaut up.  Say the cost of leaving Earth's gravity gets down to a $500 plane ticket, where are you going to put the billion's of people who leave?  How are you going to feed them?  So no, 100 years from today is not possible.
Comment: @Samuel I'll give you impossible is a little strong, but we would have to focus on it as a species to have a real chance of doing it.  Lets say we get ships that can make a round trip to mars in 2 years in the next 10.  we would have to average 25.5 Million people/year for 90 years.  Anything is possible, but Billions of people are big numbers.
Comment: @manutd Anything is possible, our best bet to get large numbers off the surface is an actual viable space elevator.
Comment: @bowlturner A hundred years is more than a lifetime, literally orders of magnitude different than 10 months. I think you're ignoring the law of accelerating returns. The world in 50 years ago was vastly different than today, the world 50 years from now is going to be even more vastly different than today. Additionally, it's certainly not impossible, at most it's only improbable.
Comment: You are vastly underestimating the capacity of a super tanker.  A *Nimitz*-class aircraft carrier has a compliment of over 5500 people.  *Allure of the Seas* has a maximum capacity of approx. 6300 people.  The largest container ships have a capacity approaching 20k TEU.  Assuming you can put 2 people in each TEU, that would be 40k people.
Comment: Also, your math is wrong.  500 million people would take 100,000 trips by boat, not 10k.  And 1 million trips by plane, not 100k.
Comment: @Nick2253 I'll take a look at my math again.  Could 40,000 people also have enough to eat and some basic sanitation with that many for 2 weeks?
Comment: @bowlturner It really depends on what you mean. Today, people try to smuggle themselves into the US by packing 10 to 20 people into a 40' container. They have meager food rations, and use buckets, but they can survive. 2 people/TEU is incredibly spacious by that measure.
Answer: As asked, the answer is no.  To reach the nearest star in 100 years it would take at absolute minimum 100,000 times more energy than the Earth currently consumes to simply accelerate and decelerate 2 billion people.  You can read all the gory details below.  So I'm going to answer an expanded question, "could a third of humanity be living off Earth in 100 years?"
I'm going to draw from existing estimates and near-future technology that's already been shown to work.  No zero-point energy, no warp or hyper drives, no wormholes, and we're not going to solve gravity.  What I will allow is more efficient and reusable rocket design, space elevators, efficient recycling, fusion power, and deep sleep chambers.

How many people are we talking?  The UN estimates the population in 2115 will be 6, 10 or 16 billion depending on how optimistic you are making it 2, 3.3 or 5.3 billion people we're getting off the Earth.  I'd like to believe if we can organize an effort to move billions of people off the planet, we can get our population growth under control, but I don't think whether its 2 or 5 billion will have a big impact.

Where are they all going?  An orbital habitat?  An uninhabitable planet in this Solar System?  A habitable planet in another Solar System?  Each of these affects two variables: the change in velocity required and the mass per person.  How much stuff do we need to ship for the population to survive?
If we send humans to a habitable planet in another solar system, that's a lot of velocity to escape the Solar System and get there in less than 100 years.  You need to send enough food, water and air for that whole time (even sleeping) plus fuel to slow you down once you get there.  However, once you're there, with a few tools you'll be self-sufficient like pioneers of old.
An orbital habitat requires the least amount of velocity, just enough to get to low Earth orbit, but since we need to build the whole thing it requires moving a lot of mass per person.  It has no resources to draw on but sunlight, and so all the food, water, soil and air will need to be shipped up.  Recycling and growing food could be self sustaining, but there will always be leaks and inefficiencies, so periodic shipments are required.
Going to an uninhabitable planet, probably Mars or maybe hollowing out some dwarf planets, requires more velocity than Earth orbit, extra fuel for landing a significant amount of mass, extra mass for machinery, shelter, food, water and air to sustain the population until they create a bubble.  Farming is a dicey proposition as there is far less sunlight that far out (moving an asteroid sufficient to house billions of people to Earth orbit is out of the question).

How are they traveling?  Depends on where they're going.  If it's Earth orbit we can allow multiple Space Elevators and Fusion Power.  Since the power is coming directly from the Earth, and fusion gives us a huge power source, it effectively negates the energy cost of putting stuff into orbit.
If it's to another object in our Solar System we can use conventional rockets, but it's going to take a lot of fuel to get there, and we're not coming back.  90% of the mass of a rocket is fuel.  We could probably get it down to about 5 tons of fuel for each ton of cargo (the difference from the 7 tons in the article is because our Space Elevator allows us to assemble our spacecraft in High Earth Orbit for free).
If we're going to another Solar System, we have new problems.  We need to escape the Sun's gravity, but that's peanuts compared to the velocity required to get to another Solar System in 100 years.  Let's say we find a new Earth in the closest star Alpha Centauri a mere 4.3 light years away.  To get there in 100 years we need to travel at 5% the speed of light or 15,000 km/s.  That's 600 times the velocity to get to Mars.  It gets worse: our hypothetical colony ship has to slow down once it gets there.

We can get some lower bounds of realism by calculating the kinetic energy required just to get 2 billion people up to the required velocities.  Forget fuel, food, air, spacecraft and inefficiencies (which will likely add 10 to 100 times more mass).  What is the minimum amount of energy required to fling the population to their target?  (It turns out we don't need to go much further in our estimates than that).
2 billion people weigh about 1.4 x 10^11 kg.  Let's plug that into the kinetic energy equation for our various needs.
Orbital Habitat via Space Elevator:  1/2 * 1.4 x 10^11 kg * (8 km/s)^2 = 4.5 x 10^18 J which is about 5% of the energy used by the US in a year.  No problem.  Even adding the mass of all the material and supplies, plus inefficiencies, this is well within our energy budget.
Other planet in our Solar System:  1/2 * 1.4 x 10^11 kg * (25 km/s)^2 = 4 x 10^19 J which is half the energy used by the US in a year.  Since the real energy required is likely orders of magnitude more, not to mention building a fleet of disposable space ships (the energy required gets far worse if they're coming back), that would be a serious problem.
Reach another Solar System in 100 years:  1/2 * 1.4 x 10^11 kg * (0.05c)^2 * 2 = 3 x 10^25 J which is 100,000 times more than the world's energy consumption so that's not going to happen.

Conclusion?  With fusion power, space elevators, and advances in recycling, farming, closed environments, and orbital construction it is plausible that a third of the Earth's population could be living in orbital habitats in 100 years.  Anywhere else is infeasible, it would simply take too much energy to accelerate that much mass plus fuel, supplies and ship.
The next question is why would you do this?  Flinging people off the planet to control population or live in a better environment is a popular trope in sci-fi, but realistically you'd be better served spending all that time, effort, organization, material and energy fixing the Earth.  The Earth, even a messed up Earth, is a far more pleasant environment than anywhere else.  You could build a  biodome or dig underground to get all the benefits and none of the drawbacks of living in an orbital habitat in space or doing the same thing on another planet without having to fling it all off the Earth.

There is a better way to get the Earth expat population up.  Send a much smaller population and then do what humans do best: make more humans.  Assuming the Earth's population stabilizes, and assuming they land on a bountiful planet, with technology allowing a low death rate and long period of fertility, a small population can grow to a significant fraction of the Earth's in a few centuries.
Comment: Let us [continue this discussion in chat](http://chat.stackexchange.com/rooms/20884/discussion-between-michael-kjorling-and-schwern).
Answer: 1/3rd of today's Earth population or 1/3rd of the future Earth's population? Most likely, it will be the future's. One easy way to be able to more easily move that many people would be to introduce some sort of catastrophic event that reduces the Earth's population to a more manageable solution.

another planet which has characteristics similar to those of earth?

With or without FTL travel? Without FTL travel, it would take much much longer than 100 years to get there, although that will be what it looks like from Earth, to the people on board, slow boating at high percentages the speed of light, it would only take much longer than 100 years. With FTL travel? They could be there already, humans on Earth could have come here from that planet, because causality
TL;DR: You would need to shift the goalposts by light years to be able to achieve your scenarios
Answer: Ignoring technology, there's another big problem.
Let's use today's population - Google says it's 7.125 billion (OK, as of 2013).
So, our goal is to move one third of that number to.. let's say Mars. It's close. That's 2.375 billion people that need to go from here to there in 100 years.
Over 100 years, that's an average of 23,750,000 people going from here to there, every single year. That's if you could start shipping people today.
So, let's cheat a bit - theoretically we could build one-way ships to Mars today (or soon enough), so we'll let you get your infrastructure up and start the clock with the first launch.
Speaking of today, dividing that by 365 days in a year gives you about 65,000 people, every single day, for 100 years, that you need to move from here to there to make your target - and that's if we don't start the clock until the first rocket launches.
For a bit of perspective - the average immigration to Canada and the US each year is 750,000 per year. You're talking about moving that amount of people every 11-12 days.
You don't have a technology problem - you have a volume problem. :)
(And even if we cheat and count births on Mars towards our billions, unless you can get a lot of people there very fast it's not going to significantly help you.)
Comment: And even with this, you're looking at that pesky thing known as [launch windows](https://en.wikipedia.org/wiki/Launch_window): one day is not equivalent to another for space travel. For going to Mars, favorable launch windows occur approximately every 2.1 Earth years. So you'd need to queue up all those people for over two years, then ship them off at once...
Comment: Oddly, I think that's probably not a limiting factor. If you have the ability to construct enough ships for 65K people/day, you just need enough space to hold the ships. And after 9 days you can completely depopulate Wyoming, which should give you some room to work. :)
Answer: Well, not the current population, but getting one person into space and killing everyone else is plausible. Of course, they might not be alive very long.
However, you don't need to get anyone in space. Killing everyone would suffice, since $\frac 1 3$ is a valid answer for $\frac 0 0$.
Comment: Clever, but not terribly interesting.  Better suited to a comment.
Comment: That does answer the question but it feel like cheating no ?
Comment: @Cort: you only need three people to have an interesting conversation: two to talk and one for them to talk about ;-)
Comment: In Dasdre's defense, I found his answer because I was checking to see if someone came up with it before I answered similarly.  Decreasing the population makes 1/3 a much easier metric, though I'm a little more civilized.  I was going to save at least 100 people.  More interesting conversation.
Comment: @SteveJessop It will be hard to repopulate the Earth that way, though. And even harder for the person on the other planet.
Answer: No. The odds are no where in the realm of in our favor.
First we'd need to find a planet similar to ours. (We're just barely beginning to find planets in other solar systems. While the number is increasing fast, we really don't know which, if any, could be similar to earth with the little data we have on them)
Then we'd have to build transport for billions of people. (Assuming you're talking about the current population, we'd need some sort of transport for 2 billion people or so. Our current space endeavors have room for a dozen at most?)
And then we'd have to get there. (This is the big kicker. Simply due the size of tne universe, the distance we'd have to travel is too vast--even at the speed of light--to reach a potential twin planet in the span of 100 years.)
100 years is just not a realistic timeline for that.
I mean, unless Matt McConaughey finds that wormhole relatively soon.
Comment: @schwern the vastness of space?
Comment: This answer needs some reasoning to back it up the assertions.


What is mind contain of?

Question: What are the contain of the mind?Are emotions being mind contain or they are from of mind energy?how does mind differ from each other?how  person being act differently.?
Answer: Here's the standard answer of what the mind is according to Buddhism. 4 aggregates.

Feelings. (Pleasant, unpleasant, neither pleasant nor unpleasant.)
Perception. (Spontaneous recognition)
Volitional formations.
Consciousness. (6 consciousnesses, 5 physical sense base consciousness and 1 mind consciousness.)

We all have the same structure of the mind. The difference from person to person is merely that different feelings at different time for different people, (only 3 possibilities)
We can possibly speak different languages, so our perception of sounds is different, I perceive Russian language sound as noise, those who knows the language perceives their meaning spontaneously.
We choose to react differently to different things, but we all have the same basic template to choose from. Metta, or anger, or generosity, or greed. Emotions fall under the category of volitional formations.
We can be conscious of different things at different times. Like he's sleeping, I am awake etc.
The mind object can be anything, including the 4 aggregates of the mind itself, it's perceived via the mind base, and when mind consciousness arise to come together, we have contact of mind object. When contact happens, feelings arises and is dependent on what contact it is, what perception we have of the contact etc.
Answer: A bit more esoteric response would be as follows:
"The Mind" that we think we have doesn't exist.
The true mind, or Buddha Mind, is one that is shared between all sentient beings and is pure, clear, true and excludes nothing. It does not require zazen to be still, it does not lack enlightenment. It is this mind that we experience in deep samadhi.
Answer: I think this is an interesting video about: His Holiness the Dalai Lama talks on the "Nature of the Mind"
I find it a very interesting point of view, also because is very similar to the most advanced knowledge that we have in neurosciences.
Hope it helps!
Answer: It is the combination of Thoughts and Mental factors that creates the mind, however, the brain and consciousness also a requirement for the sense sphere to function which finally gives rise to experience the awareness of the five aggregates of existence.

What is mind contain of?


ZFS and cache devices

Question: I'm going to add a SSD drives to my ZFS storages as a cache. Anyone has any experience with this? What if cache device dies, will the any data be affected?
Answer: Basically there's three types of ZFS cache, all used for both data and metadata.

ARC (Adaptive Replacement Cache) - Main memory DRAM cache for reads and writes.
L2ARC (Level 2 ARC) - safe read cache: no data loss/service interruption from device failure.  Usually SSD based.
ZIL (ZFS Intent Log) - safely holds writes on permanent storage which are also waiting in ARC to be flushed to disk.  Data should rarely live in this cache for longer than 30secs and data is never read except after a crash to replay any uncommitted pool writes.  On recent any recent ZFS version, Zil device failure won't cause data loss (all data still in ARC), but device failure + a crash or power outage may cause some writes to get lost.

Upgrade your ARC first, buy oodles of main memory. Note L2ARC and Zil both have overhead allocated out of the ARC too.
L2Arc is populated by read-cached blocks as they are evicted from ARC.  ZFS by default only caches random IO (small reads) into L2ARC and is not used for streaming workloads (unless instructed to).  You can basically use any device for this (including a fast 15k HD) but it works best with an SSD that handles many random read IOPS with ease.
ZIL accelerates workloads which require synchronous writes (processes wait for confirmation that writes have actually been committed to disk before continuing execution).  Zil performs a similar role to battery backed cache on high end RAID controllers.  Although write latency and streaming write IOPS are what define a good Zil SSD, a Zil above all else mustn't ever loose any data in the event power loss. Many suitable devices have a super-capacitor to finalize any pending operations without system power.   SLC SSDs with high write endurance (Intel X25-E) used to be recommended, but newer devices use RAM with battery/supercap to write back to NAND in the event of a power failure. ZILs need not be large, but by using only a small fraction of a large device (e.g. 8GB out of a 300GB Intel 320 MLC SSD) you can yield much higher effective write endurance.  'Enterprise' vendors always recommend mirrored ZILs, my workloads have never been that important.
As for specific products, STEC made the first SSDs for Sun's Fishworks project (both Logzilla & Readzilla) and has current devices for both ZIL (ZeusRAM $2500/8GB) and L2ARC (Zeus IOPS $3k/400GB) which both come highly recommended.  PCIe based SSDs are also worth considering, like the ZIL-specific DDRdrive x1 ($2k/4GB) or any big PCIe SSD for L2ARC. Other less performant (read:cheaper) 2.5inch SSD devices can also offer significant performance gains especially when used in aggregate for L2ARC.
Comment: OCZ Vertex2Pro is MLC NAND, but unlike almost every other SSD it has a supercap allowing writes in progress to complete when power is pulled. DDRdrive X1 is 4GB DDR2, 4GB SLC and a supercap that copies ram to NAND in 60secs when power is lost.  Logzilla is write optimized SLC NAND with a supercap (no DDR either)
Comment: u sure OCZ Vertex2 is ddr based? I see it's nand-mlc based
Comment: thanks, I have 2 kingston (intel-based) ssds which I gonna use as a cache devices until they die or warranty will be over. then look at your suggestions.
Answer: http://web.archive.org/web/20100911224754/http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide
(The Solaris Internals website no longer up but WebArchive has a copy)

ZFS and cache devices


Why does the viewfinder of the Nikon D90 have a 4×4 grid instead of 3×3?

Question: I was amazed that viewfinder of my camera has a 4 x 4 grid.  Why is this? There's no 3 x 3 grid. Sad. What is the reason to did it so? Is it possible to fix it (upgrade software of camera)? What cameras do have 3 x 3 or golden ratio grid?
Answer: See this on the golden ratio and this on the rule of thirds. In short, these "rules" aren't very well supported as rules, and Nikon's assumption might be that they're unlikely to be very important to someone buying a mid-level DSLR. The even division has the advantage of showing you the center nicely, and simply having more lines is nice for alignment because it's more likely that something linear in the scene will correspond.
You can't change this in software, as the lines are physically on the screen. I don't believe Nikon makes official replacement, but you can get third-party focusing screens from KatzEye Optics with various grids, including "Rule of Thirds Grid" and various crop lines for 8×10 or square format or etc. If you really would like golden ratio grids, they'll do that too as a custom option.
Alternately, it looks like the corner focusing point indicators are on or very close to thirds; you can use that for composition instead.
Comment: brilliant! thank you for your answer! this is what I was looking for
Answer: I'll argue that it's about perception: I don't see a 4x4 grid when I look through the viewfinder, I see three horizontal lines and three vertical lines. Where the lines intersect create the "rule of thirds" guidelines.
Comment: The intersections create rule of thirds guidelines only if you accept that 1 ÷ 3 is ¼. :)
Comment: I think, it's better to switch OFF it and do it on my own perception :)
Comment: @mattdm Doesn't the roughly 95% viewfinder coverage make it close enough to 1/3? :)
Comment: Close enough for _me_. I think it's a silly rule. :)


Screen lock not working in Moto z play

Question: I recently got into an issue with my Moto z play screen lock. Pressing the power button doesn't lock the screen. I have enabled pattern lock option for screen lock. But still only after booting up it asks for the pattern. But later on when I lock the screen by pressing power button , I can unlock by just swiping the screen. Anyone knows what's the issue?
Answer: It could be (depending on your Android version) there is an extra option called

powerbutton locks immediately

if that is not selected it could be the problem. You could crawl the security settings for more options.
Comment: `power button instantly locks` this option I have already enabled
Answer: It was be because of the Google smart-lock feature. The on-body detection was on in settings->security->smart lock
. I Turned off the on-body detection and its fine now

Screen lock not working in Moto z play


Multiple Protection Enchantments

Question: Is it possible to stack multiple protection enchantments on the same piece of armor? (an armor piece with both protection and blast protection, for example)
Answer: You cannot get two Protection enchantments on one item with vanilla enchantment or using books. You can do this using the /give or /summon command though (this command will give the nearest player iron leggings with Protection III and Feather Falling I):
give @p iron_leggings 1 0 {ench:[{id:0,lvl:3},{id:1,lvl:1}]}

Look at another answer to get more information how the command works.
The enchantment IDs can be found on the Minecraft Wiki.
Answer: No. A piece of armour can only have one type of protection on it in vanilla Minecraft. (Feather Fall on boots is not counted as a protection for this.)

Multiple Protection Enchantments


CoreAnimation stack going crazy

Question: I've been asked to help fix a bug for a client, who is an inexperienced developer. However, I'm absolutely stumped by this one.
The problem is that after a string of opening and closing a view controller, which is being pushed onto a navigation controller, all of the subviews will disappear (including the navigation bar items) and show straight through to the window. After this happens, I can still press the buttons on the navigation bar, but they will immediately disappear on touch-up, and restoring a stable UI state is impossible without a quit & relaunch. Another obscure side effect is that after closing the app, Springboard will flash as I swipe between screens. My initial thoughts were that this was a memory issue (e.g. subviews getting released on memory warning), but I have since cleaned all the leaks & checked all the viewDidLoad/viewDidUnload handling of outlets and the problem is still happening. So now I think that with the Springboard effect, that the code is somehow messing up the state of core animation entirely.
Has anyone seen anything like this before? Or have any idea how it would be possible to make this much of a mess? I would attach some screenshots, but trying to take a screenshot with the phone when the app is in this state causes a system crash.
Answer: I've not experienced this, but maybe a memory warning is eating some of your views?
I know that iOS is free to unload view controllers that aren't visible.
I'd stick a breakpoint in viewdidunload or similar and see if that triggers.
Answer: As it turned out, this bug was caused by a UIView being deallocated while it had a superview.

CoreAnimation stack going crazy


eligibility for transit visa

Question: I hold an Egyptian passport and am traveling from Cairo to London via Turkish Airlines. I will have a long layover more than 12 hours.
Do I need a transit visa? or shall I enter Turkey getting a transit visa on arrival at the airport. I have a valid visa to England
Answer: A search in Timatic gives the following result:

Transit - Turkey (TR)
TWOV (Transit Without Visa): Passengers with a confirmed onward ticket for a flight to a third country within 24 hours. They must stay in the international transit area of the airport and have documents required for the next destination.

So you don't need a transit visa. (I am assuming that you will indeed be staying in the international transit area in Istanbul, i. e. both flights are on the same booking.)

eligibility for transit visa


Electrical Load increase on Generator = More Fuel Consumption

Question: Why does more electrical current drawn from generator leads to more fuel consumption? I understand that it's due to conservation of energy, I just want to know what the phenomenon or reaction is called that leads to more power being transferred to the engine via the gears.
Answer: The generator has a speed governor.
As electrical load increases the mechanical load increases. If the throttle position were fixed the speed would drop. The governor opens the throttle to allow more fuel in to maintain speed at setpoint.

Figure 1. Mechanical speed governor. Source.
Figure 1 shows an old-fashioned mechanical governor.

As the shaft rotation speed increases the flyweights are thrown outwards, lift the control sleeve against the speeder spring and drive the crank to shut off the fuel valve.
If the shaft slows down the speeder spring pushes the control sleeve back down and the crank opens the fuel rack again.
Spring pressure is controlled by the speed control lever to set the running speed.

Modern speed regulators are electronic. They monitor the output frequency and adjust the fuel valve electrically.
Answer: The increased output current in the generator windings increases the magnetic field strength which opposes rotation of the generator shaft. To maintain the same RPM (and thus maintaining frequency and voltage) the engine throttle must be opened further, using more fuel.
Answer: Here is a more detailed account of the energy conservation involved.
The generator output power is given by Power (watts) = Voltage (volts) X Current (amps). For AC, there are two additional multipliers, power factor to account for the phase relationship between voltage and current and the square root of three for a three-phase generator. Voltage is regulated to a constant value. Current and power factor vary with load.
The generator converts mechanical power to electrical power. Mechanical power is given by Power = Torque X Rotational Speed. An additional multiplier may be required depending on the units of measurement used. Speed is normally regulated to be a constant value in order to keep the voltage an frequency constant. Torque varies as required to supply the mechanical power that is converted to electrical power.
The engine speed is regulated to maintain a constant generator speed. If the generator requires more torque, the fuel flow must increase to supply the additional power. Power available from burning fuel is proportional to fuel mass per unit of time. The throttle regulates the mass rate of fuel flow.
Answer: For any electromechanical device, the electromagnetic torque or force produced is directly proportional to the current flowing through them, if the excitation field is unchanged. A generator has its torque opposing that produced by the engine (or whatever is turning the generator). The engine requires energy to turn the shaft against the torque of the generator, much like you need energy to lift a weight vertically against earth's gravity.
When the load draws more current, more generator torque is induced due to the higher currents, the engine faces more resistance to its motion, just like how you would feel when you are lifting a 10 kg mass and someone adds another 5 kg mass to what you already have. The speed (of the generator and you) would drop as a result (which is not good), so the control system sends additional fuel to bring the speed back.
Answer: Loading: If the load on a power system is increased, the load current on the system increases, which results in increased armature current in the generator. This increased armature current results in an increased magnet field in the armature. The rotor (field magnet) located in this armature magnetic field will then experience more attractive force which will in effect reduces the speed of the rotor, which in turn reduces the voltage. As the speed reduces the frequency in the system also reduces.  N=120F/P. This reduction in rotor speed is sensed by the turbine governor. To keep the speed and frequency constant at 50hz, the governor valve will be opened and the turbine output power is increased to restore the generator voltage and frequency.
Unloading: If the load on a power system is reduced, the load current on the system reduces, which results in decreased armature current in the generator. This reduced armature current results in a reduced magnet field in the armature. The rotor (field magnet) located in this armature magnetic field will then experience a less attractive force which will in effect increases the speed of the rotor which in turn increases the voltage. As the speed increases the frequency in the system also increases.  N=120F/P. This increase in rotor speed is sensed by the turbine governor. To keep the speed and frequency constant at 50hz, the governor valve will be closed and the turbine output power is reduced to restore the generator voltage and frequency.


Is it possible to have high energy compaction in audio signal?

Question: We all know that the energy compactness in image can be achieved in high scale.But in case of audio signal is it possible to have such high energy compactness?
Comment: Image and audio are concept with little shared understanding. If you were given random images, energy compactness  wouldn't be achieve, even at high scale. Could you please be a little more specific?
Answer: Depends on what you mean exactly by "energy compaction".
Most audio signals are "pink" in nature, so doing any type of frequency transformation will "compact" the energy towards the lower frequencies and most audio codecs use this property. Not sure you get "high" energy compaction: a typical FLAC compression rates are about 30% size reduction or so.
It's more difficult to compact a signal in time through some sort of linear transformation or invertible transformation. This would really depend on what exactly you are trying to do and what the general properties of your signal are.


BMW E90: Professional Radio (Alpine CD73) USB Adapter won't work

Question: I bought an USB Adapter which emulates a CD Charger. The port wasn't used yet. When I plugged my battery the Radio worked, but I couldn't find the CD charger /USB in my radio source menu. Do I have to code the Radio? If yes which tool and codes do I need? Thank you!
Comment: Forgive my ignorance, but the Alpine is the original equipment? Or is this something you put in as an aftermarket head unit?
Comment: The radio is a bmw standard radio for e90
Answer: According to installation instructions for a cd changer retrofit on an E90 linked here, yes you will need to code the car for it.
Coding the car will require an INPA OBD2 cable (purchased on Amazon, eBay, etc.) and the appropriate BMW progman software. Some INPA cables will come with software, but it's usually best to get the latest versions. If you have a Windows XP laptop laying around that's the best platform to install the progman/ediabas/INPA software bundle, which also enables fun things like checking trouble codes, inspecting sensor outputs and registering a new battery.
WARNING: Be extremely careful if you choose to code your car yourself! It is entirely possible to "brick" your car. Find instructions on coding through the E90 forums or this link and follow them to the letter. If any of this concerns you, please contact your nearest dealer to get the car coded appropriately.
Comment: I was in my vendor's garage, and he had a look for the coding. It didn't work. Seems that the adapter won't work with my radio.
Comment: Does your adapter tie into the MOST fiber optic ring? There is only one adapter I know of that does and it's in the $500 range...
Answer: The problem here is that I have a Professional radio with MOST interface. To adapt an USB interface, you have to buy an adapter which also has MOST. Such an adapter is e.g. the Dension Gateway 500, see this link: Dension E90 Professional (without Navi) pre-facelift. These devices are much more expensive as the adapters without MOST interface (>300 €)


Does TCP improve the ability of IP to send really really large files?

Question: How does TCP improve the ability of IP to send really large files? Show me the math. (Calculate the max packet that IP can send and multiply by the maximum fragments. Compare that to what TCP can do.)
Comment: You may want to read up on what the different layers of the TCP/IP model do.
Comment: based on your parenthetical... this sounds like homework. Is it? ...homework is explicitly off-topic here. If so, please delete this quesiton. Thanks.
Comment: @CraigConstantine How disgusting is the idiotic rule to deny a good question if it happens to be a homework.
Comment: 'disgusting' seems a strange word to use; I presume this means it IS homework, so I've closed it. None the less, welcome to our community, where the members decided what topics/questions would be consider on/off topic. You can refer to the Help Center and you're welcome to post in the Meta site if you want to discuss wether your question is on or off topic.
Answer: IP is a layer-3 protocol, and TCP is a layer-4 protocol. Neither protocol understands files. An application will send data to layer-4 (TCP), and TCP will break the data into chunks and encapsulate it in TCP segments. TCP will pass the segments to layer-3 (IP), which in turn encapsulates the segments in packets. IP will pass the packets to layer-2 (ethernet), which encapsulates the packets in frames. Ethernet will then pass the frames to the hardware (driver) which serializes the frames to bits on the wire.
TCP is one of many layer-4 protocols. It is a connection-oriented protocol which creates a bi-directional conversation with TCP on the other end. TCP provides guarantees for delivery and reassembly of out-of-order segments, and this is why it is often used for files transfers, but an application could use something like UDP, which doesn't have any guarantees. With UDP, the application must take on the responsibilities to get all data and reassemble it into the correct order.
This Wikipedia article may help you understand the OSI Model.
Answer: TCP provides three features that IP alone does not have:

Guaranteed delivery.  If a packet is lost, TCP will detect and
resend it.
Packet ordering.  If packets arrive out of order, TCP can
reassemble them in the correct order.
Transmission rate control.  TCP allows the receiver to tell the sender to slow down or speed up as necessary.
Answer: Actually TCP run atop of IP (ie. you can't run TCP exclusively without IP).
Long story short: multiple protocols are involved during a file transfer, and the assumption that TCP/IP is always better (than UDP/IP for instance) for large file transmission can be technically not exact.
This is because, as said above, we have many protocols involved (have a look at http://docs.oracle.com/cd/E23823_01/html/816-4554/ipov-6.html#ipov-7), and each one of them can implement features in an exclusive, complimentary or even duplicate way with respect to each others.
Practical example:

FTP: run atop of TCP/IP, it's reliable in case of unreliable networks (when there is rumor, when devices or links over the Internet fail, etc.)
TFTP: run atop of UDP/IP, it's easier by design, it's totally unable to manage unreliable networks (and situation in which packets are not delivered in the proper order) but it has less overhead

If you're transferring files in your local - reliable and deterministic - LAN you will probably require less time with TFTP than FTP, but if something goes wrong the result will be a corrupted file or a connection abort (requiring you to restart everything and lose more time).
Even if questionable from a real point prospective, no one will stop you from using UDP and than write an application protocol that implements the features of TCP, like retransmission, windowing, congestion avoidance, etc.
Nowadays, btw, I would say that the most promising protocol is WEBDAV (HTTP), that runs on TCP/IP.
But going back to your question my answer would be: TCP can be considered a better choice for developing an application protocol for large file transfers, because it has some built-in features that we can use out of the box, like:

Congestion avoidance: if a link become congested the 2 peers can dynamically lower the speed
Sequencing: if packets containing the payload of a file cross different paths and arrive at destination in a different order, TCP can rebuild the payload properly
Error management: actually managed complimentary with other protocols, if part of the transmission is lost or corrupted, a retransmission of those data is automatically performed


how to make object read only without using profiles or permissionset?

Question: how to make object read only without using profiles or permissionset??
Is there any setting or configuration in salesforce which makes object access as read only for all users except admin. I have created custom object Invoices in salesforce and want to make that object as readonly when that gets deployed using package link in another org ??? Any kind of  help or suggestions are really appreciated......
Answer: Object access depends on two settings: Profile/Permission Set Object settings, and the Deployment Status setting on the object itself. This means that any object you create through the UI has either one of two states: Available to only administrators ("In Development"), or available with full access to everyone (all profiles gain all CRUD permissions, but is controlled by the sharing model).
Even using the metadata API, the best you can do without profiles is to give access to nobody at all, similar to the access you'd get with "In Development", but at a profile level. You will necessarily need to adjust the profile settings if you want to prevent users from creating their own records, or deleting or editing records they own, or are granted permission through parental sharing. There's no one-stop shop for creating an object that all users have only read-only access to initially without crafting a metadata call to that effect or manually editing all the profiles.
This is doubly true for packaged objects. The administrator at the far end must choose the security they'd like to use, which means the sharing model is completely outside your control at that point. You can't give an organization an object and not give them full control to determine what level of access users will have to the objects.
Answer: A Trigger or Validation Rule can block saving of records based on the Profile of the saving User.
Validation Rule:
<code>($Profile.Name != "System Administrator")
</code>
This, unfortunately, may allow a user to think that they are creating an Invoice, but at least it won't allow them to save it. This is a last resort, but if you can't count on Profiles to be configured properly, it will still work.
If you are concerned your Validation Rule may be deactivated, you can use the same logic in an Apex Trigger, it just takes a little more work to do the same thing: block saving unless the user's profile is the correct one.
Comment: Good point Jeremy, and I agree "This is a last resort, but if you can't count on Profiles to be configured properly, it will still work."
Comment: Thanx for the replya Jeremy. I appreciate the information you given. I can use it in some other area. But actually it is not good practice to allow user to enter the record information and then wont allow him to save. That what i am thinking, might your idea would work for other case but for me it would not.
I will tell you what i did to make object ReadOnly ,
Answer: 2 classic answers :

send the record through an approval process which freezes the record : this is great and works very well, can also be automated with a trigger which starts off the approval process
a more soft way is to change the record type to switch the presentation page to all field reand-only. This doesn't make the record read-only, but is a very good approximation.

Do these work for you ?
Rup
Comment: I've done the record type solution before with a page layout that makes the fields appear "read only". Great when you know the business users only access via the web page (not via API or other tools).
Answer: Thanx for the replya Jeremy and all others. I appreciate the information you given. I can use it in some other area. But actually it is not good practice to allow user to enter the record information and then wont allow him to save. That what i am thinking, might your idea would work for other case but for me it would not.
I will tell you what i did to make object ReadOnly ,
I have created custom VF page for tabview of object and New button is excluded from that page , This makes whole object New button hidden behind the VF page. So user not even able to enter record information . And for edit and delete button as well as for action link of the same , I have created custom vf page which give message like "you dont have permission to edit or delete record" . And overrided that page on button and action link of edit and delete. This help me to disallow the record inline edting also.


How close $k$-sums of a random set of numbers are on average?

Question: Consider a set of random iid variables $x_1, \ldots x_n$ uniformly distributed on $[0, 1]$. For each $S \subset [n]$ with $1 \leq |S| = k < n$ take $\sigma_S = \sum_{i \in S}x_i$. Obviously $\sigma_S$ are distinct with probability 1. What is the expectation of $\Delta = \min_{|S| = |S'| = k, S \neq S'} |\sigma_S - \sigma_{S'}|$, at least asymptotically? Can we say something about concentration of $\Delta$?
Comment: Seemingly a loose (trivial) upper bound could be get by calculating $E[(\sigma_S-\sigma_{S'})^2]$.
Answer: Here is some heuristics, which should be possible to strengthen to a completely rigorous answer.
Note that $\sigma_S$ is the sum of the sample of size $k$ taken with replacement from the (random) empirical distribution corresponding to the iid sample $x_1, \ldots x_n$ from the uniform distribution on $[0, 1]$.
For large $n$, this empirical distribution is close to the uniform distribution on $[0, 1]$. Also, if $k=o(\sqrt n)$ (which let us assume), then sampling with replacement differs little from sampling without replacement. So, the distribution of $\sigma_S$ (with $S$ considered a random subset of $[n]$ of size $k$) is close to the distribution of the sum of $k$ iid random variables (r.v.'s) uniformly distributed on $[0, 1]$, which, by the central limit theorem, is in turn close to $N(k/2,k/12)$ if $k$ is large, which let us assume as well.
So, the distribution of the vector $(\sigma_S\colon S \subset [n],|S| = k)$ is close to that of the vector $(X_1,\dots,X_N)$ of $N:=\binom nk$ iid r.v.'s each with a distribution close to $N(k/2,k/12)$.
Let $U_j:=F(X_j)$, where $F$ is the cdf of $N(k/2,k/12)$, so that the $U_j$'s are approximately iid uniformly distributed on $[0, 1]$
and hence the random vector $(U_{(j)}-U_{(j-1)}\colon j=2,\dots,N)$ of the spacings between the consecutive order statistics based on the $U_j$'s approximately equals in distribution $(V_2,\dots,V_N)/(V_1+\dots+V_{N+1})$, where the $V_j$'s are iid r.v.'s each with the standard exponential distribution. By the law of large numbers, $V_1+\dots+V_{N+1}\sim N$. So, $(U_{(j)}-U_{(j-1)}\colon j=2,\dots,N)$ is close in distribution to  $(V_2,\dots,V_N)/N$.
On the other hand, the minimum of $|X_i-X_j|$ over all $i\ne j$ equals $\min\{X_{(j)}-X_{(j-1)}\colon j=2,\dots,N\}$, where the $X_{(j)}$'s are the order statistics based on $X_1,\dots,X_N$.
Now write
\begin{equation*}
 U_{(j)}-U_{(j-1)}=F(X_{(j)})-F(X_{(j-1)})
 \sim(X_{(j)}-X_{(j-1)})F'(X_{(j)})
\end{equation*}
\begin{equation*}
 =(X_{(j)}-X_{(j-1)})F'(F^{-1}(U_{(j)}))
 \sim(X_{(j)}-X_{(j-1)})F'(F^{-1}(j/N)),
\end{equation*}
whence, with $\tau:=F'\circ F^{-1}$,
\begin{equation*}
 X_{(j)}-X_{(j-1)}\sim\frac{U_{(j)}-U_{(j-1)}}{\tau(j/N)}
 \sim\frac1{\tau(j/N)}\frac{V_j}{V_1+\dots+V_{N+1}}\sim\frac{V_j}{N\tau(j/N)}.
\end{equation*}
Next,
\begin{equation*}
 E\min\{\frac{V_2}{\tau(2/N)},\dots,\frac{V_N}{\tau(N/N)}\}
 =\int_0^\infty \prod_{j=2}^N P(V_2>\tau(j/N)x)dx
\end{equation*}
\begin{equation*}
 =\int_0^\infty \exp\Big(-\sum_{j=2}^N \tau(j/N)x\Big)dx
 =\frac1{\sum_{j=2}^N \tau(j/N)}\sim
 \frac1{N\int_0^1\tau(u)du}=\frac{\sqrt{\pi k/3}}N,
\end{equation*}
by using the substitution $u=F(z)$ in the integral $\int_0^1\tau(u)du$.
So, it should follow that
\begin{equation*}
 E\min\{X_{(j)}-X_{(j-1)}\colon j=2,\dots,N\}
 \sim \frac1N\,E\min\{\frac{V_2}{\tau(2/N)},\dots,\frac{V_N}{\tau(N/N)}\}
 \sim\frac{\sqrt{\pi k/3}}{N^2}
\end{equation*}
and hence
\begin{equation*}
 E\min_{|S| = |S'| = k, S \neq S'} |\sigma_S - \sigma_{S'}|\}\sim \sqrt{\pi k/3}\Big/\binom nk^2.
\end{equation*}
Comment: This is very interesting, thanks! I still have a few concerns:

1) If $k >> \sqrt{n}$ almost all pairs of $\sigma_S$ are dependent due to birthday paradox. Could if affect the result significantly?

2) I am not much convinced about approximating normally distr. variables with uniformly distr. ones, especially in light of order statistics where tail distribution may weigh in. Can you clarify why this is a decent approx.?

3) Could you please cite a source on difference of order statistics being equally distr. with functions of exp. distr. variables?
Comment: @MikhailTikhomirov : 1) This concern may be valid, and it may turn out that the restriction $k<<\sqrt n$ is needed for the heuristics to go through. 2) I have added comments on what could be done without the "approximation" (anyway, the tails should matter little, as the spacings $X_{(j)}-X_{(j-1)}$ are greater there, given the distribution of $X_j$ is close to normal). 3) Concerning the spacings for the uniform distribution, this can be done by straightforward distribution transformation technique; see e.g. Theorem 6.6 in \url{http://bit.ly/2wkcw2f}.
Comment: The constant factor in the asymptotics is now specified to be $\sqrt{\pi/3}$, and the heuristic "approximation" of the normal distribution by a uniform one is completely eliminated.


Why is fertilizing suggested as a way to crowd out weeds?

Question: Empirically I trust that this must have worked, but I'm curious why good fertilizing is often suggested as a way to promote turfgrass growth to crowd out weeds. Why don't weeds benefit from the fertilizer?
Answer:
Why don't weeds benefit from the fertilizer?

They could, depending on the weed. But the grass benefits more.
Most weeds are opportunistic. They germinate and flourish where the grass is thin or absent. If one keeps the grass healthy, which includes watering, fertilizing, and not cutting it too short, the grass will fill in and shade weeds and their seeds, minimizing their spread.
I'll note that even in a healthy lawn, it's impossible to ensure against weeds 100%. But when the lawn is in good shape, it's very easy to keep up with the weeds, pulling them as needed.
Comment: Thanks! From your description, it sounds like the starting point is a reasonably healthy lawn, in which case fertilizing would be good to maintain its dense growth and to prevent weed invasion. However, if one has a bad lawn, where weeds have already taken hold in many places -- then I assume fertilizing would not help as much to crowd out weeds before one deals with weeds first?
Comment: It's always easier to start with a healthy lawn. But fertilizing is still part of restoring a lawn that needs help. You can't _just_ fertilize. If there are weeds, the lawn will recover much better if you remove them instead of hoping for the grass to do it. But fertilizing will make the weed-removal effort more effective.


ASP.NET: Clustered environment communication Problem

Question: I'm pretty noob with ASP.NET programming and i'm a bit confused on a problem that i'm facing right now.
We, as devs in my company, live in a clustered environment like the one shown in figure

Nothing really special.
You see, IIS Websites are duplicated on evry FrontEnd Servers. Business logic resides on BackEnds that are sitting, togheder with DB and NAS File system, behind a firewall.
So communication between the public space and the protected one is permitted only through particular channels, with particular requests, to particular IPs and Protocols.
Now, we were asked to build a site where the user can customize his own environment, upload images that will be dispalyed in his HomePage and other features.
In a classical configuration, a user upload an image that is written in a folder in the site root, and then the HTML refers to that image to populate whatever control to display it.
But, when a user connect to our site, the load balancer will choose one particular frontend that's not the same for evry session.
So, a user will upload his file, disconnect and then come back only to find that his image is gone, 'couse the Load Balancer has routed his request to a differnt frontend where the image does not exist.
So the need to write a piece of code that pull the file from the NAS behind the Firewall.
The upload part is stupid, and i can understand it.
My problem is:
when the user connects to his page, how i reference in the HTML an image that's not on the machine the site is running on but on a completely hidden File system?
I thought of writing a WCF that serve the image as as a byte stream, but which ASP.NET control to use on the Page to put the stream content on, and How?
I Know that asking the experts community will bring me the best way to accomplish this.
Hope this is clear enough.
Thanks so much for the replays and excuse me for the bad english form.
Comment: Do you guys see the image?
I cannot see it, but I'm behind WebSense and I'm not sure if it's blocking it or there were upload problems.
Comment: The image displays fine for me.
Answer: Instead of using your file system for User Images, i would recommend you to go for some CDN solution like Amazon S3 or some other you like. This way you don't need to take care of where the image is stored or requested from, it shall always be accessed through CDN url(given when you upload an image on CDN programmatically), where url shall be in your database.Using a CDN releives you of many concerns that you shall face while storing at your location.
Even though if you don't like to use S3 , then your option is good enough to develop a simple WCF/WEB service to upload/serve the images.
Comment: This sure been a nice answere if only were not given 2 years later :)


How to set static IP on ubuntu 14.04

Question: I am using ubuntu 14.04 system. Please anyone can tell me how to set static IP address on my system.
Comment: Or http://askubuntu.com/q/338442/158442
Answer: command line way:
To set a static IP edit /etc/network/interfaces and change the following:
auto eth0
iface eth0 inet dhcp

to:
# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet static
address 192.168.0.150
netmask 255.255.255.0
gateway 192.168.0.1
network 192.168.0.0
broadcast 192.168.0.255
dns-nameservers 220.127.116.11 18.104.22.168

Obviously, you will want to change eth0 to whatever your network card is called (hint: ifconfig) and change your IP address, gateway, dns-nameservers to whatever you want them to be. Now, if you want your DNS to come from your ISP then don't set any and it will work fine.
Finally, restart your ethernet:
sudo service networking restart
sudo ifdown eth0
sudo ifup eth0

Graphical way:
open system settings > network > Wired > Options
it will look like this:

set Method to Manual
click Add under Address and fill various fields.
Set DNS if you know if, leave blank if want it from your ISP. save
plug-in your ethernet cable
check your ethernet is working or not by ping google.com if you are getting output then success
Comment: @zoro if it helped you so accept it

How to set static IP on ubuntu 14.04


Can this ultrafilter convergence condition be expressed as a compactness condition?

Question: Suppose that $X$ is a topological space. Let us say that an ultrafilter $\mathcal U$ on the Boolean algebra $C_X$ of clopen subsets of $X$ is partition-prime if whenever $X = \amalg_{i \in I} X_i$ is a clopen partition of $X$ we have $X_i \in \mathcal U$ for some $i \in I$.
The set $X'$ of partition-prime ultrafilters on $X$ forms a topological space under the usual Stone topology with basis $[V] = \{ \mathcal U \in X' \mid V \in \mathcal U\}$ for $V \in C_X$, and we have a continuous map $\eta \colon X \to X'$ sending $x$ to $\{ V \in C_X \mid x \in V \}$. This is clearly the reflector onto a certain full subcategory of topological spaces; the game is to figure out which one.
It is easy to see that $\eta$ is injective just when $X$ is totally disconnected, and that $\eta$ is a subspace inclusion just when $X$ is zero-dimensional Hausdorff. We would like to know when, moreover, $\eta$ is surjective, and hence a homeomorphism.
This will happen precisely when each partition-prime ultrafilter on $C_X$ is of the form $\eta(x)$ for some $x \in X$. It is easy to re-express this condition (under the assumption that $X$ is zero-dimensional Hausdorff) as saying that $\eta$ is surjective precisely when each partition-prime ultrafilter on the full powerset $\mathcal P X$ converges.
My question is whether there is a natural way of re-expressing this convergence condition as a compactness condition. The obvious guess is that this is the same as ultraparacompactness: every open cover of $X$ can be refined to a disjoint clopen cover.
It is not so difficult to show that our convergence condition is implied by ultraparacompactness. Indeed, if $X$ is ultraparacompact, and $\mathcal U$ is a completely partition-prime ultrafilter on $\mathcal P X$ with no convergent point, then the open sets not in $\mathcal U$ cover $X$; we can refine this cover to a disjoint cover $X = \amalg_i X_i$; and so $X_i \in \mathcal U$ for some $i$, contradicting the fact that $X_i \subseteq U$ for some open $U \notin \mathcal U$.
The other direction is much less clear. Suppose $X$ is zero-dimensional Hausdorff and ultraparacompact, and suppose towards a contradiction that $X = \bigcup_i U_i$ were an open cover with no disjoint refinement. Clearly it does no harm to assume that this is a cover by clopens, and the assumption of no disjoint refinement implies in particular that there is no finite subcover (since a finite cover by clopens can always be refined to a disjoint one). So the sets $V_i = U_i^c$ generate a proper filter $\mathcal F$ with no adherent point. Moreover, any clopen partition $X = \amalg_j X_j$ must fail to refine the cover $(U_i)_{i \in I}$, and so there must exist some part $X_j$ of the partition which meets each set in $\mathcal F$. Clearly, this is a necessary condition for $\mathcal F$ to be extendable to a partition-prime ultrafilter. If it were also sufficient we would be done: for then we could choose a partition-prime $\mathcal U$ extending $\mathcal F$ which, since $\mathcal F$ has no adherent point, would not converge: a contradiction.
So, my claimed characterisation of the property that every partition-prime ultrafilter converges as ultraparacompactness would follow if we could prove the following ultrafilter lemma:

If $\mathcal F$ is a proper filter such that for any clopen partition $X = \amalg_j X_j$
there is some $X_j$ which meets each set in $\mathcal F$, then there is a partition-prime
ultrafilter extending $\mathcal F$.

An obvious attempt at a transfinite argument works well at successor stages, but falls over at limit ordinals. So there remain three possibilities: this is true; this is false; this is independent of the axioms of set theory, and I don't know which of these it is.
Another way of looking at this ultrafilter lemma is via locale theory. Given any locale $L$, we can obtain a new locale $L'$ by taking sheaves on the Boolean algebra of complemented elements of $L$, for the topology whose covers are all clopen partitions. Now $L \to L'$ is a reflector into zero-dimensional ultraparacompact (aka "strongly zero dimensional") locales. Clearly the passage $X \mapsto X'$ described above sends $X$ to the space of points of the strongly zero-dimensional reflection $\mathcal O(X)'$: which would thus be ultraparacompact so long as $\mathcal O(X)'$ were spatial.
Now clearly not every strongly zero-dimensional locale is spatial (take any atomless complete Boolean algebra). But it's possible that the strongly zero-dimensional reflection of any spatial locale is spatial, and this is in fact exactly equivalent to the ultrafilter lemma I quote above.
Any ideas, either about the ultrafilter lemma, or about a different characterisation of the spaces of the form $X'$, would be gratefully received!
Comment: Thanks, yes, I meant clopen subsets. Edited to correct
Answer: Your condition amounts to saying that the uniformity $\mathcal{C}$ generated by all clopen partitions is complete: 'partition-prime' is the same as '$\mathcal{C}$-Cauchy'.
It is also implied by the condition that the space is $\mathbb{N}$-compact, which means that every clopen ultrafilter with the countable intersection property is fixed: if $\mathcal{U}$ is $\mathcal{C}$-Cauchy then it has the countable intersectionproperty; if $\{U_n:n\in\omega\}$ is a decreasing sequence in $\mathcal{U}$ with empty intersection (and $U_0=X$) then $\{U_n\setminus U_{n+1}:n\in\omega\}$ is a clopen partition with no member in $\mathcal{U}$.
In New properties of Mrowka's space $\nu\mu_0$ Kulesza showed the space $\nu\mu_0$ from the title is $\mathbb{N}$-compact; it is not strongly zero-dimensional, hance not ultraparacompact.


Tag "movement": Should we rename it to "movado"?

Question: The question title says it all—shall we rename the tag "movement" to "movado" (which is Esperanto and more specific to the Esperanto movement and distinguishing it from other movements)?
Comment: It's worth considering using Esperanto in *all* tags, not just this one.  But it certainly seems appropriate for this one at least.
Comment: @nathaniel: I am also thinking of "tabelvortoj" instead of "correlatives" since this is the technical term. Otherwise, I am fine with a mixture of English and Esperanto tags.
Answer: Since it is referring to the Esperanto movement, I would use movado.
I am not totally sure we need such a tag, but between movement and movado it is preferable the later. The former is too generic, and it should be replaced by esperanto-movement; since esperanto should not appear on our tags, movado is the only alternative I see.
Answer: It seems strange to me that just this one tag should be translated to Esperanto and thus movado. I personally think we should only have English tags unless we want to translate every tag and have twice as many tags for every question. Unless I'm missing something, if the tag movement is used in the Esperanto StackExchange, it certainly refers to the Esperanto movement. I'm against using the tag movado.
Comment: I agree with this. Movado literally just means movement. I think you would use the word movado for example to talk about any sort of movement if you were speaking Esperanto. It's no different from if you were in a green political conference and you said "the movement" without specifying which movement you were talking about - it would be obvious that you are talking about the green movement.
Comment: One point for clarity – in all these cases, we'll want to have "synonym" tags that point to the "root" tag.  So if someone enters "movement" as a tag, it will give them "movado" (or vice versa).  We'll thus be able to ensure that only the preferred tags get used.  The process of determining which ones are "preferred," of course, is the tricky part.
Answer: The word movement is vague, it can be a physical movement, or any kind of movement. With the word Movado it is clear that it is about the social movement that aims to propagate Esperanto in the whole world. The "Esperanto-movement" in English can be not understood as "movado", it can be understood as "everything in Esperanto", which is not good as we already have more precise tags for that.
Since the tag is too vague, I suggest that we divide movement into at least three tags (examples) :

movado, for questions about organisms and methods to propagate the use of EO
culture, for questions about the Esperanto culture
speakers, for questions about Esperanto speakers (demography, fields of usage etc.)

This way, we will benefit more from the precision given by the tags.


Linking data to road colour scheme

Question: I'm getting started with a QGIS map showing the quality of roads in my town. I have various data which create an index of 1-5.
How do I link this index data to road data in a map, showing the bad roads (5) in red, and good roads (1) in green?
Comment: How is your index data related to the roads?  ie use your common identifier field to execute a join.
Answer: What you're trying to create is either a categorized or graduated symbology.  This website walks you through it: http://qgis.spatialthoughts.com/2012/02/tutorial-styling-vector-data-in-qgis.html
Answer: It seems like your trying to create a spatial matrix on your road layer from other intersecting layers.  To populate the road layer you will need to perform either a combination of Join Attribute by Location, Spatial Query, or Union.
Spatial Query - will select one table features based on spatial intersection parameter.  You may find the tool in the Vector menu>Spatial Query>Spatial Query.
Join Attribute by Location - will join the two tables together based on spatial intersection.  You may find the tool in the Vector menu>Data Management>Join Attribute by Location.
Union - You should be mindful of that the joining of spatial data between polyline and polygon data is not always a one to one relationship, since sometimes polyline features overlap polygon features.  Union tool is located in the Vector menu>Geoprocessing Tools>Union.
With each method you will most likely have to clean up your final database eliminating un-wanted fields and devising a matrix schema for each criteria (or field) that may add up to the total classified field (summation of the other criteria fields).

Linking data to road colour scheme


Error while working on authentication of one drive "KeyError: 'expires_in'"

Question: I am trying to connect to onedrive and download files to my local. But when i try to do authentication i am getting error.
Traceback (most recent call last):
  File "/Users/rishi/PycharmProjects/pythonProject1/venv/testing2.py", line 37, in <module>
    graph_client.login()
  File "/Users/rishi/PycharmProjects/pythonProject1/venv/ms_graph/client.py", line 262, in login
    self.grab_access_token()
  File "/Users/rishi/PycharmProjects/pythonProject1/venv/ms_graph/client.py", line 308, in grab_access_token
    token_dict=token_dict
  File "/Users/rishi/PycharmProjects/pythonProject1/venv/ms_graph/client.py", line 144, in _state
    ) + int(token_dict['expires_in'])
KeyError: 'expires_in'

Process finished with exit code 1

I have used the code provided in github. After login and giving permission, i copied and pasted the link, after that i got this error. Could anyone help me where i went wrong.
I have used the steps provided in youtube.
Comment: Please provide your feedback here if you get any idea or suggestion  here >>[https://feedback.azure.com/](https://feedback.azure.com/forums/34192--general-feedback)
Answer: Looks like there is some configuration error while setting up the expiry time in client.py class.
Please try logout and sign-in again.

Check if any value (other than 0)of expiry parameter is set(in expires_in   parameter of access_token which of type int). See if access token is  empty.
The default lifetime of an access token varies, depending on the
client application requesting the token. When the access token
expires, the client must use the refresh token to (usually silently)
acquire a new refresh token and access token.
You can adjust the lifetime of an access token to control how often
the client application expires the application session, and how often
it requires the user to re-authenticate. You could update or create a
new connection to the connector before the Flow Access Token Expires.

See -Information about active-directory-configurable-token-lifetimes
and Configure-token-lifetimes,get-started
Reference:
One drive Authentication and sign-in-MS Docs


What happens if Shepard died in Mass Effect 2?

Question: Can you still import the save? If so what happens?
Comment: Then you can't play ME3. The game disc disintegrates upon loading. Way to go.
Answer: You cannot import the save if your Shepard did not survive the events of Mass Effect 2. That Shepard's story ends with their death. Mass Effect Producer Casey Hudson has stated the following:

Dead is dead. Mass Effect 3, as with the rest of the trilogy, is Shepard's story. If you have a dead Shepard at the end of Mass Effect 2, that saved game won't import into Mass Effect 3. You can play Mass Effect 3 if you died in Mass Effect 2 of course, but you'll have to create a new Shepard. Harsh? Yes. But we wouldn't be serious about the concept of a suicide mission if you couldn't die and your death didn't have serious consequences.
Comment: Dead is dead, unless it's in a cutscene at the beginning of ME2.
Answer: If Shepard died in Mass Effect 2, you will not be able to import that save.
Source
Answer: You cannot import a save where Shepard has died.


Neptune's eccentricity stability

Question: Will Neptune's orbital eccentricity remain lower than earth's forever?
It currently is at around 0.008, compared to Earth's 0.0167.
Answer: Earth's Eccentricity varies between about 0.000055 and 0.0679.  This is the first Milankovich cycle.  When Earth' eccentricity is at its lowest, it is lower than that of Neptune.

The Earth's orbit approximates an ellipse. Eccentricity measures the departure of this ellipse from circularity. The shape of the Earth's orbit varies between nearly circular (with the lowest eccentricity of 0.000055) and mildly elliptical (highest eccentricity of 0.0679).4 Its geometric or logarithmic mean is 0.0019. The major component of these variations occurs with a period of 413,000 years (eccentricity variation of ±0.012). Other components have 95,000-year and 125,000-year cycles (with a beat period of 400,000 years). They loosely combine into a 100,000-year cycle (variation of −0.03 to +0.02). The present eccentricity is 0.017 and decreasing.

4Laskar J, Fienga A, Gastineau M, Manche H (2011). "La2010: A New Orbital Solution for the Long-term Motion of the Earth" PDF. Astronomy & Astrophysics. 532 (A889): A89. arXiv:1103.1084
Comment: @uhoh indeed. This doesn't answer my question, only gives a lovely background of the question if you ask it about Earth
Comment: The very first sentence here does answer the question, though.
Comment: Without saying something about what Neptune's orbit will do in the long term, this is not yet an answer. The title of the question is "**Neptune's eccentricity stability**" and in the body the OP asks "**Will Neptune's orbital eccentricity** remain lower than earth's forever?" **But this only talk about Earth's orbit** likely because a Wikipedia page for Earth's orbit was easy to find. This is a helpful comment only. `-1`
Comment: @RoryAlsop the question is about the *time variation* of Neptune's eccentricity; "Will Neptune's orbital eccentricity remain lower than earth's forever?" The first sentence in this answer takes Neptune's eccentricity as a constant, exactly the opposite of what's asked.
Comment: No, it doesn't say anything of the sort @uhoh. You have interpreted it to say it's a constant, but that is just your assumption.
Comment: @RoryAlsop there are four lights
Answer: tl;dr: It will be around the year 14,800 that Earth's eccentricity drops below that of Neptune's.
It's unusual to post two answers, but this one is sufficiently different that in this case I think it's better as the contents and comments they may attract may be quite different.
Lucky for us the one of the JPL development ephemerides' latest releases goes out beyond AD 17,000!  See Ryan S. Park et al 2021 AJ 161 105 The JPL Planetary and Lunar Ephemerides DE440 and DE441.
Also lucky for us the Python package Skyfield can download and interpolate the ephemerides for us in an easy to use way.
However once we have state vectors (position and velocities) rather than orbital elements, we need to decide what "eccentricity" means. Orbital elements assume Kelperian trajectories and what we have is numerically integrated solutions to an n-body problem.
So I'll use an ad hoc definition $e = (r_{max} - r_{max}) / (r_{max} + r_{max})$ and look at two distances; heliocentric and barycentric.
We can't use osculating orbital elements since those are constantly changing within a single orbit.
Here are the results. Every 200 years I calculate Neptune's position twice a year (total of 332 times per orbit) and every 50 years I calculate Earth's position once a day (367 times per orbit) then apply the equation above to get the two eccentricities.
The result agrees qualitatively with my other answer, but since I show more accurate numerical data rather than ballparking the plots, I can now say that it will be around the year 14,800 that Earth's eccentricity drops below that of Neptune's.

<code>from skyfield import api
import numpy as np
import matplotlib.pyplot as plt

loaddata = api.Loader('~/Documents/fishing/SkyData')  # avoids multiple copies of large files

ts = loaddata.timescale() # include builtin=True if you want to use older files (you may miss some leap-seconds)
eph = loaddata('de441.bsp')

sun = eph['sun']
earth = eph['earth barycenter']
neptune = eph['neptune barycenter']

# Neptune
years_neptune = np.arange(2000, 17001, 200)
yearz = np.arange(0, 165.6, 0.5)
e_neptune_bary, e_neptune_helio = [], []
for year in years_neptune:
    y = year + yearz
    times = ts.utc(year + yearz, 1, 1)

    x_bary = neptune.at(times).position.km
    r_bary = np.sqrt((x_bary**2).sum(axis=0))
    e_bary = (r_bary.max() - r_bary.min()) / (r_bary.max() + r_bary.min())
    e_neptune_bary.append(e_bary)

    r_helio  = neptune.at(times).observe(sun).apparent().distance().km
    e_helio = (r_helio.max() - r_helio.min()) / (r_helio.max() + r_helio.min())
    e_neptune_helio.append(e_helio)

e_neptune_bary = np.array(e_neptune_bary)
e_neptune_helio = np.array(e_neptune_helio)

# Earth
years_earth = np.arange(2000, 17001, 50)
days = np.arange(367)
e_earth_bary, e_earth_helio = [], []
for year in years_earth:
    times = ts.utc(year, 1, days)

    x_bary = earth.at(times).position.km
    r_bary = np.sqrt((x_bary**2).sum(axis=0))
    e_bary = (r_bary.max() - r_bary.min()) / (r_bary.max() + r_bary.min())
    e_earth_bary.append(e_bary)

    r_helio  = earth.at(times).observe(sun).apparent().distance().km
    e_helio = (r_helio.max() - r_helio.min()) / (r_helio.max() + r_helio.min())
    e_earth_helio.append(e_helio)

e_earth_bary = np.array(e_earth_bary)
e_earth_helio = np.array(e_earth_helio)

if True:
    fig, (ax1, ax2, ax3) = plt.subplots(3, 1)
    ax1.plot(years_neptune, e_neptune_bary, label='barycentric')
    ax1.plot(years_neptune, e_neptune_helio, label='heliocentric')
    ax1.set_xlim(1950, 17050)
    ax1.set_ylim(0, None)
    ax1.legend()
    ax1.set_ylabel('eccentricity')
    ax2.plot(years_earth, e_earth_bary, label='barycentric')
    ax2.plot(years_earth, e_earth_helio, label='heliocentric')
    ax2.set_xlim(1950, 17050)
    ax2.set_ylim(0, None)
    ax2.legend()
    ax2.set_ylabel('eccentricity')
    ax3.plot(years_neptune, e_neptune_bary, label='Neptune barycentric')
    ax3.plot(years_earth, e_earth_helio, label='Earth heliocentric')
    ax3.set_xlim(1950, 17050)
    ax3.set_ylabel('eccentricity')
    ax3.set_xlabel('Year')
    ax3.set_ylim(0, None)
    ax3.legend()
    fig.suptitle('DE441, e = rmax-rmin / rmax+rmin', fontsize=14)
    plt.show()
</code>
Answer: Answer supported with sources to

Will Neptune's orbital eccentricity remain lower than earth's forever?

tl;dr: No, in about 10,000 years Earths' will go below Neptune's, which stays above it's current value for the next ~400,000 years.

It is hard to consider "forever" for two reasons:

"forever" is a long time
While numerical integration can be arbitrarily accurate, the inputs needed to model the solar system (e.g. exact positions and velocities at $t_0$ and masses) can't be ascertained, and the calculation integrating from now until "forever" (or at least until the Sun expands and eats the Earth) is extremely long.

@JamesK's answer cites a source that suggests Earth's eccentricity oscillates at several frequencies and will range between about 5.5×10-5 and 6.8×10-2.
The orbital evolution of the Sun–Jupiter–Saturn–Uranus–Neptune system on long time scales (also here) show Neptune staying fairly low in eccentricity for 2 million years, but never going anywhere near as low as Earth is expected to.
No. Not "forever" and not even for very long!
So for the next two million years or so, Neptune's eccentricity will remain in the same ballpark, whereas Earth's will repeatedly dip way below it.

From here showing that Neptune will stay above it's current 0.008 eccentricity for at least 400,000 years.

below: Cropped from Milankovitch Cycles Orbit and Cores and annotated to show Neptune's minimum for the next 400 kiloyears.
It looks like in very roughly only 10,000 years Earth's eccentricity will dip below that of Neptune's.
Comment: Thank you for the informative answer! If Neptune's eccentricity won't stay as it is forever, what's its lowest and highest?
Comment: @איתימרלוב my answer explains why "forever" can't be addressed. What you're asking can't be answered.
Comment: If this cannot be answered, can you at least tell me which planet in our solar system excluding Mercury through Mars has the eccentricity that varies the least overtime?
Comment: @איתימרלוב That's a **different question than what you've asked here**, so it's better to post that a new question. But "over time" is too vague just as "forever" is impossible. The DE411 ephemeris that I used in [this answer](https://astronomy.stackexchange.com/a/47189/7982) spans the years -13,200 to 17,191 so we have reliable information there. Outside of that one has to do a lot of poking around looking at various papers that might not agree with each other. That's probably more work than it's worth for me, but if you post as a new question then others may want to give it a try.

Neptune's eccentricity stability


How to reduce current

Question: I need help reducing current in my motor driver. The chip is the L293D motor driver with output max 600mA. My stepper motors draw maximum 350mA per phase and operate at 12V, so I am concerned about overcurrent. Is this ok to do, or do I need to add resistors? I looked at some other questions similar in askings, but not the answer I was looking for. The power supply is switching between 8 AA batteries and a wall wart that supplies 5A @ 12V. I am concerned because I wonder if I would need to limit the current at all, and if needed, what do I do. I am also thinking about if I use the batteries, since they are rated in Amp-Hours, the circuit could draw only the needed current. I don't know. Please Help!
Answer: If the stepper motor only draws 350mA max, it will only ever consume that much (and probably only at high loads). The driver is capable of supplying 600mA, but that doesn't mean it's going to insist the motor uses it all!
There should be no overcurrent problems from the motor's perspective, and I would expect the driver IC to have in-built protection to prevent more than 600mA being drawn if the motor were to take leave of its senses and go crazy.
Any rudimentary current-limiting may just add unnecessary drain on the batteries, or have a detrimental effect on the circuit in general. The whole point of a motor controller is to eliminate these sorts of headaches
Answer: Assuming your stepper motor windings are rated for 12V continuous you should not have a problem (though it may run quite warm).
If your windings were rated for (say) 6V, you would get a potential performance boost by running the from a 12V drive with a series resistor. The maximum ramp rate would be improved, at the expense of throwing away a lot of power in the series resistors. Since you have a 12V motor and a 12V supply, you can't do that, in fact the best you'll be able to do is probably a bit less than 10V at 350mA, since the driver eats a volt and change at either rail (and turns it to heat).

How to reduce current


Accidental Presses With Smart Keyboard Folio

Question: I plan to buy the iPad Air with the Smart Keyboard Folio and Apple Pencil soon. I noticed that if you're using the iPad flat on a surface, the keyboard is essentially face-down into that surface. Can anyone who own a Smart Keyboard Folio tell me if using the iPad like this and pressing the screen causes the keys on the keyboard to accidentally press against the surface? Thanks.
Answer: The keys are disabled when you flip it over - so accidental presses is not a problem there.
Comment: Oh, I forgot about that!!! Thanks. Hard to tell when you don't have it in front of you


datatype supplied by user for SQL field

Question: I have a SQL table which has a number of fields
ID | Value | Type
A typical record may be :-
1000,10,[int]
a second row may be:-
1001,foo,[string]
a third row may be:-
1002,10/12/2008,[DateTime]
I have been asked to look at this as at the moment, each time we wish to select from this table we have to cast the value to the type specified. I am able to do a database redesign on this and am wondering the best route to go to optimise this. (SQL 2000).
Answer: Horrors!  This is the dreaded Entity-Attribute-Value (EAV) model! Run away!
But seriously, assuming there is some reason for needing this kind of model, maybe create a properly typed column for each data type?
ID       Type      StringValue       DateValue      NumberValue
1001     String    Foo
1002     Date                        10/12/2008
1003     Number                                     123.46

Answer: Generally when designing tables you want to know what is actually going to be in them. Do you have a distinct number of data types which you need to support? Do you need to cover decimals? One possible solution would be something like this:
CREATE TABLE dbo.My_Table (
     id           INT NOT NULL,
     data_type    VARCHAR(10) NOT NULL,
     string_value VARCHAR(100) NULL,
     int_value    INT NULL,
     date_value   DATETIME NULL,
     CONSTRAINT CK_My_Table_data_type CHECK data_type IN ('int', 'string', 'datetime'),
     CONSTRAINT PK_My_Table PRIMARY KEY CLUSTERED (id)
)
GO

You can then use the data type to decide on which column you want to select or insert/update. Keep in mind though that you might have problems with using:
SELECT
     id,
     CASE data_type
          WHEN 'string' THEN string_value
          WHEN 'int' THEN int_value
          WHEN 'datetime' THEN date_value
          ELSE NULL
     END

SQL Server requires that the data types all match for a column being returned. If you are only ever selecting one at a time it might work ok, but if you ever want to select sets of data then you'll likely need to do some casting anyway or select only rows where the data_type values are equal. I haven't done testing on all of the scenarios though, so you should play around with it to see what works and what doesn't work.
I'll just say again though, you should look at the design of your application again. It's certainly possible that you have a requirement for this kind of functionality, but often times when I see this design pattern what the front-end REALLY wants is a string that will be displayed in the application. That string just happens to look like a number or a date at times. If you're going to actually be performing data type specific functions on the data then it's likely that a less "flexible" design is called for, but without knowing all of your requirements I can't say. This is just from my experience in the past.
EDIT: Looks like I type too slowly and Tony beat me to it. :)

datatype supplied by user for SQL field


Choosing a reference letter recommender

Question: When choosing a recommender for a graduate fellowship application, do people generally request a reference letter from the professor in whose class they received A's? I am considering asking one of two professors for a reference letter for a fellowship application. I took a 1-credit professional skills course in which I received an A in, and in the other more academic 3-credit course, I received a B. However, I have had a few conversations with the professor who teaches this 3-credit course. Generally, in any circumstance regarding a fellowship application, which recommender would people generally choose, the professor in whose course they received an A in or the professor whose office hours they have visited?
Comment: I wonder this too. Of course, I do have classes in which I received an A in and had some interactions with the professor.Could we perhaps attach a resume and maybe a cover letter of some sort to help the professor should he agree to write you a LoR?
Answer: You want a recommendation from somebody who can speak to your strong qualities.  This means faculty members you have interacted with; the more substantial the interactions, the better.  However, you also want the interactions to have demonstrated your existing skill and future potential.
If you took a one-credit class from a professor and have had little interaction with them otherwise, they probably cannot write you a strong letter.  The one-credit class probably had more limited interactions between you and the instructor.  if you were very active in class, that would be good.  But if you were not an extremely active questioner and class participant, that means the professor will have very limited basis for evaluating you (especially since one-credit classes tend to have rather little homework on the basis of which you can be evaluated).
In contrast, a professor you have taken a full three-credit course from and also interacted with outside class will probably have a much better idea what your skill level and potential are.  The downside is obviously that you earned a lower grade in the class.  Unless you had a lot of in-class interactions with the first professor, I think you should get in touch with the second professor and simply ask them whether they can write you a strong recommendation.  If they say they cannot, I would go with the first professor.  Otherwise, I go with the second professor.
Comment: First - second - first etc.  It's confusing.  Could you edit and say "The A Professor" or "The one-credit professor"?

Choosing a reference letter recommender


Magento 2 : Add Product functionality in frontend

Question: Does anyone know about module availability/custom module implementation which allows me to add product same as admin panel from frontend, as i have a requirement to implement it in frontend as per the client specification.
Comment: Probably extension you need doesn't exist jet ;c
Comment: Any custom implementation suggestion or reference ....like any admin panel form functionality implemented in frontend?
Answer: Here is the module you can get
https://codecanyon.net/item/magento-2-add-product-from-frontend/19930429


Generally, what kind of non-academic misconduct can make a student get expelled?

Question: We all know a student is expelled because he committed something extremely bad. But how is extremely bad? Must the student commit a crime or something? Unfortunately, university policies do not give details of that.
(In America and Canada)
Comment: This will be highly dependent on country and university. E.g. having sexual intercourse in the lavatories of a christian university in the US might get you expelled but will have no consequences in a regular german university. I therefore vote to close.
Comment: Many relevant Q&A on here, this is but one : https://academia.stackexchange.com/q/28966/72855
Comment: Likewise, reporting that you were a victim of sexual assault will get you expelled from BYU, but in other places, people might investigate the crime.
Answer: As an undergraduate, I served on the disciplinary hearing board for a large private secular university in the United States. I saw the full spectrum of cases that came before the board, from minor infractions to severe violations of university policy (and the law).
In my experience, the university was reluctant to fully expel someone. Minor infractions typically resulted in some form of mandatory training and/or disciplinary probation. Repeated minor infractions might result in a short suspension. For most severe policy violations (e.g., assault), the university preferred to hand out lengthy (1-2 year) suspensions rather than permanently expelling the student. Obviously, I'm sure that many students chose not to return after this setback.
The exception to this was sexual assault cases, which provoked a more unequivocal response from the university. Expulsion was certainly on the table for cases where a student was determined to have committed sexual assault. At the very least, the perpetrator would be suspended as long as the victim remained on campus, to ensure that the victim did not have to interact with the perpetrator. Inevitably, Title IX requirements and liability concerns shape both the hearing process and the outcome for sexual assault cases. This type of scrutiny was generally absent from other cases.
I can think of one other case where the hearing board recommended expulsion for a student. In that case, the student dealt tens of thousands of dollars of hard drugs to an undercover police officer over many months. The student was arrested and the university subsequently began an internal hearing process.
The standards and process may differ for other types of universities, but generally I got the sense that my experience was representative of other large secular universities in the United States.
Comment: Good answer! Can you please add an explanation of "Title" IX"?
Comment: Can the university do anything to a student who has not yet graduated but already finished the degree and left the university?
Comment: @problemofficer Title IX is a federal law in the United States that ensures gender equality in universities. It is probably best known for improving women's sports offerings, although recently it has played a large role in addressing sexual assault and sexual harassment on campus. The Wikipedia page for "Title IX" explains it better than I can.
Comment: @Rapidturtle I'm not sure that I understand your situation but the outcome will depend on the location and type of university that you're attending. It will also depend on the nature of the infraction. If I had to guess, I would say that the university would probably be reluctant to pursue it if you're no longer a presence on campus.


Allow user to update/delete certain policies(Hashicorp Vault)

Question: Description
I am using Hashicorp's Vault ,version 1.7.0, free version.
I would like to allow a certain range of policies that a user can assign/delete to a group. In that way he can add or delete entities user to the group from the UI.
What I have done
Bellow is written into blocks the overall policy file.
{
capabilities = ["list"]
}

#To show the identity endpoint from the UI
path "/identity/*"{
 capabilities = ["list" ]
}

#policies that I would like the user to have the ability to #assign to the group.

path "/sys/policies/acl/it_team_leader"{
capabilities = ["read", "update", "list"]
}

path "sys/policies/acl/it_user"{
capabilities = ["read", "update","list"]
}

path "sys/policies/acl/ui_settings"{
capabilities = ["read", "update", "list"]
}

path "sys/policies/acl/personal_storage"{
capabilities = ["read", "update","list"]
}

#Group id that the user have full access

path "/identity/group/id/2c97485a-754f-657a-5a8b-62b08a3ce8cb" {

capabilities = ["sudo","read","update","create","list"]
}

What is the issue
Lets assume that I have an super-privileged policy that provides access to the the whole secret engine.
From the UI I am able to assign to that group the super-priveleged policy and basically allow a restricted user to assign this super policy to the whole group.
When I extended the policy with :
path "sys/policies/acl/**super-priveleged**" {
capabilities = ["deny"]
}

is just restricting the policy to be read from the UI.
Appending the group path with allowed_parameters such us :

capabilities = ["sudo","read","update","create","list"]
denied_parameters = {
"policies" = ["it_user","it_team_leader",etc]

}

I receive a permission denied error(403).
Appending with denied parameters :
path "/identity/group/id/2c97485a-754f-657a-5a8b-62b08a3ce8cb" {

capabilities = ["sudo","read","update","create","list"]
denied_parameters = {
"policies" = ["super-policy"]

}

is not functioning and I am still allowed to assign the super policy.
I also tried wildcards with the same result.
Is it even possible to restrict one/a range of policies that can be assigned from the Vault UI?
Thanks in advance if you made it so far.
Answer: Found the solution, to restrict user to update certain policies the allowed parameters fields should encapsulate a list and add an asterisk key with an empty list.
Note : The order of the policies assigned from the UI should comply with the order that is written in the .hcl file.
path "/identity/group/id/2c97485a-754f-657a-5a8b-62b08a3ce8cb"
{

capabilities = ["sudo","read","update","create","list"]
allowed_parameters = {
"policies" = [["policy1","policy2","policy3"]]
"*" = []
}
}


error I can not see my webpage

Question: [24-May-2017 18:10:44 America/Detroit] PHP Warning:  mysql_close() expects parameter 1 to be resource, boolean given in /home/migps/public_html/gpsenmexico/system/database/mysql.php on line 67
Comment: This is a question for stackoverflow.com but I'll give a quick answer. The only things that can be closed are things that are open of the same type which in your case is an active mysql connection.
Answer: Firstly, mysql_ is deprecated now.  You should be using PDO or at the least mysqli_
Be that as it may, you are missing the connection  e.g. mysql_close($conn)

error I can not see my webpage