Wikipedia:Reference desk/Archives/Computing/2011 July 13

Welcome to the Wikipedia Computing Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

July 13

Output of Image

(I have been bold and assumed this is a separate question. Please correct me if I'm wrong. I have also added a title (In which I could be wrong). Thank you, General Rommel (talk) 00:00, 13 July 2011 (UTC))

Hi I was wondering how the 5th line is true in picture shown on the page http://en.wikipedia.org/wiki/Combinational_logic.

i.e T F F output is T. doesnt the product of the T x F x F a false?

Chaituchill (talk) 23:44, 12 July 2011 (UTC)

Yikes, that section is about as badly written as it could be. The point of the example is that it is possible to represent any truth table using that technique. In other words, each "Result" in the truth table could be T or F, independently of the other "result"s -- you get a formula that produces that pattern of T's and F's by oring together all of the and-expressions whose results are T. Looie496 (talk) 06:22, 13 July 2011 (UTC)

5,000 BTU air conditioner in a ~150 sq. ft. room

I have the unit on max but the room doesn't get near freezing. Is this normal or is this like-new unit not very good? I do have the door open and the next room, whose air doesn't mix much with that in the rest of the house, is not air conditioned, but still... Imagine Reason (talk) 00:13, 13 July 2011 (UTC)

I can't give you a full answer (so hopefully someone else can), but you definitely need to have the door closed (as well as any windows). When you have it open all the cool air will literally seep out and mix (and then become warm) which severely dampens the results. Close the door and run it flat out for about 20 minutes, you'll probably feel the difference then, especially if you then leave the room. Of course it will depend on what the temperature of the room/outside temperature is as well as the actual dimensions of the room (ceiling height etc) so if you can give better dimensions (rather than just total square foot) I know that'll help the next person out who might be able to give a better answer.  ZX81  ^talk 01:01, 13 July 2011 (UTC)

You pretty much need to close the door for this sort of thing to work. Air masses of different temperatures will mingle a lot more than you think.

In addition to closing the door, make sure you don't have any ventilation ducts that are blowing in air from the rest of the house.

Is it a window unit? Or an upright? 5,000BTU should be fine for a 150sq ft room (With the door shut!) if it's a window unit. It's kind of borderline for an upright unit. (I'm not sure why the upright units are so much less effective.)

Finally, make sure you've got the thermostat on the A/C set properly. Most of them will shut themselves off (or switch to fan-only) mode long before the room gets literally freezing. But it should be possible to get it down into the 60s or perhaps even 50s. APL (talk) 03:53, 13 July 2011 (UTC)

Unless you have very well insulated walls, ceiling, floor, doors and windows, a unit of this rating will not be sufficient to get the temperature down to near freezing in summer, but it should reduce the temperature to perhaps 20 or 30 degrees below the surroundings if doors, windows and other ventilation inlets are all closed. Dbfirs

Even a like-new unit should have a plate on it giving the specs (or you could try downloading the spec sheet from the company website). That should state its minimum temperature, which is likely to be no lower than about 60 F. Why do you want it lower than 72 F are you opening a morgue? If its a free standing one with an exhaust pipe, then you do need a little ventilation with the out-side to replenish that being pumped out.Also, close the binds or curtains as an amazing amount of radiated heat can come through the windows.--Aspro (talk) 08:26, 13 July 2011 (UTC)

Domestic air conditioners usually have a hot air exhaust - it is where the heat that was in the room is dumped. Of course, that hot air needs to be dumped outside the room you are trying to cool. If not, you are just moving the heat around the same room and using up electricity. Astronaut (talk) 15:20, 13 July 2011 (UTC)

The BTU is a good match (though just a tad low) for the square feet. You really want around 7,000BTU for 150sqft. As for checking the AC, you need a thermometer where the cold air comes out of the AC. That is the temperature of the cold air. Your room will not get lower than the temperature of the cold air produced by the AC. So, if it is pumping 75 degree air out, you cannot cool the room below 75 degrees. If the air is not cold enough, you could need to charge the coolant or get a new AC. -- kainaw™ 13:02, 14 July 2011 (UTC)

Yes, definitely faulty if the air is coming out at 75 degrees (unless your room temperature is 100 degrees). The outlet temperature should normally be 50 degrees or below, but is unlikely to be close to freezing unless the intake air is cool. Dbfirs 17:52, 15 July 2011 (UTC)

And, even then, I think it would ice up and stop working before getting the room temperature down anywhere near freezing. This is because humidity in the air would condense on the cold parts and then freeze, eventually blocking air flow. To get the temperature that low, you'd need an air conditioner specifically designed for that purpose, as in the ones used in meat lockers. I imagine they have a defrost cycle to clear the ice build-up, like in a refirigerator/freezer combo. StuRat (talk) 18:51, 15 July 2011 (UTC)

One hint, use a large fan aimed at the side of the front of the unit to blow the cold air away from the A/C unit and bring warm air to it (the built-in fans are rather underpowered). This will prevent it from getting too cold at the thermostat, which causes the compressor to kick off. And, as others have said, close the door. This not only lets cold air out and warm air in, but also allows humidity in, which reduces the efficiency of the A/C (it's using much of the energy to condense water, not to cool the air). You might also find that it cools better when it's raining out, since that allows the external "radiator fins" to cool down more quickly. You could replicate this by spraying constantly with a hose, or maybe setting up a sprinkler, although, of course, you will soon have a puddle underneath. Most A/C units try to do this directly, by using condensed water, but don't do as good a job as a hose would. StuRat (talk) 18:51, 15 July 2011 (UTC)

How to use Queue with multiprocessing in python

I'm trying to use a queue with the multiprocessing library in Python. After executing the code below (the print statements work), but the processes do not quit after I call join on the Queue and there are still alive. How can I terminate the remaining processes?

Thanks!

def MultiprocessTest(self):
  print "Starting multiprocess."
  print "Number of CPUs",multiprocessing.cpu_count()

  num_procs = 4
  def do_work(message):
    print "work",message ,"completed"

  def worker():
    while True:
      item = q.get()
      do_work(item)
      q.task_done()

  q = multiprocessing.JoinableQueue()
  for i in range(num_procs):
    p = multiprocessing.Process(target=worker)
    p.daemon = True
    p.start()

  source = ['hi','there','how','are','you','doing']
  for item in source:
    q.put(item)
  print "q close"
  q.join()
  #q.close()
  print "Finished everything...."
  print "num active children:",multiprocessing.active_children()

— Preceding unsigned comment added by Legolas52 (talk • contribs) 04:34, 13 July 2011 (UTC)

The remaining processes aren't terminating because you aren't terminating them. joining on the queue only waits until the queue is empty; it doesn't do anything to the workers. So the simplest modification to what you have is to keep a list of the workers as you create them, and once the queue join is done you call each worker's terminate() method. Note that immediately after calling their terminate method those children will still show up in the process table (and thus in .active_children()) because the daemons' ordered closedown happens asynchronously. Much of this is simplified if you use multiprocess.Pool, which allows you to create and terminate workers (and manages work for them) and itself keeps track of the workers. -- Finlay McWalter ☻ Talk 11:55, 13 July 2011 (UTC)

Blog for selling toys?

hi Iam miki. I am intrested in making toys. And i have blog. Now i want to sale toys through my blog. But I don't know how to integrate gateway for ordering and payment. Help to add an interface to take orders and payment on blog (blogger). — Preceding unsigned comment added by 117.214.21.232 (talk) 09:19, 13 July 2011 (UTC)

You can integrate Google Checkout (Google's shopping platform for merchants) with Blogger; in your case you'd set up the items in Google Checkout and then add a "buy now" button (see this Google explanation) which sends visitors off to the Checkout pages. -- Finlay McWalter ☻ Talk 12:00, 13 July 2011 (UTC)

You might look at Etsy if you're not already familiar with it. Depending on the kind of toy you're making, it might be useful for you. APL (talk) 18:24, 13 July 2011 (UTC)

I don't think a blog would be very effective for selling toys. What you need is for your toys to be part of a large catalog of toys (or several), where anybody loooking for that type of toy (say "wooden train") would find it easily. The chances that people looking for your product will happen to read your blog is fairly low. (Although, if your blog was a widely read one on the topic of wooden trains, then it might work.) StuRat (talk) 18:36, 15 July 2011 (UTC)

'Bad Mac Read' SSL Error

Resolved

 – Sorted!

Since I put ZoneAlarm's free firewall on my system, I have been getting dialogue boxes saying:

• An error occurred during a connection to [gmail]. SSL received a record with an incorrect Message Authentication Code. (Error code: ssl_error_bad_mac_read)

I get them primarily when trying to check my Gmail, whether using Firefox (i.e. in the browser) or Thunderbird (my email client). I have tried this with ZoneAlarm on, and ZoneAlarm off, and I still get the dialogues - every couple of minutes. Uninstalling ZoneAlarm is a project in itself, so before I do that, is there any way I can stop these messages (i.e. fix this ssl error) in the meantime? --KägeTorä - (影虎) (TALK) 10:38, 13 July 2011 (UTC)

EDIT - It also happens with Google Chrome, so this is not a Firefox/Thunderbird problem. --KägeTorä - (影虎) (TALK) 11:02, 13 July 2011 (UTC)

Not that it is necessary to ask, but how did you solve it? General Rommel (talk) 11:35, 13 July 2011 (UTC)

I used RevoUninstaller to uninstall ZoneAlarm Free, and it worked without a hitch. After a restart, and a cmd console screen for five minutes (cleaning.....), everything was fine. Wi-fi card still works, no ssl errors, nothing. --KägeTorä - (影虎) (TALK) 11:42, 13 July 2011 (UTC)

how do people make web comics?

how do most large web comic authors produce their web comics? (I mean what software and hardware). I'm asking about the actual status quo. Of course, I could just scan something in from paper, and perhaps that's how they do it? Thanks. 188.28.227.240 (talk) 11:16, 13 July 2011 (UTC)

Adobe Illustrator is pretty good for producing comic-book style images, as are GIMP and Photoshop, and numerous other drawing softwares, such as Autodesk Sketchbook Pro. --KägeTorä - (影虎) (TALK) 11:39, 13 July 2011 (UTC)

For more information, see Digital illustration and List of vector graphics editors. --KägeTorä - (影虎) (TALK) 11:45, 13 July 2011 (UTC)

A good deal of them these days use graphics tablets for the actual drawing. I've no idea whether that is status quo or not. I also know that a number of them draw them by hand (like old-fashioned, non-web comics) and then use the computer primarily for inking. --Mr.98 (talk) 14:09, 13 July 2011 (UTC)

Just about any way you can think of! I'd point you to the book How To Make Webcomics, but that spends only about a chapter on actually making the comics, and the rest about the non-artistic sides of operating a website and business.

Here is a video showing how Jeph Jacques draws Questionable Content. He works almost all digital.

And here is a video (Accelerated and narrated) showing how Dave Kellet draws Sheldon (webcomic). He does things entirely the old fashioned way.

Both of these artists are popular enough to make a living with their comics. APL (talk) 18:32, 13 July 2011 (UTC)

URL bar

Using windows xp and firefox. The URL bar should be showing en.wikipedia.org/refdesk... but it shows google.com/http://www.facebook.com. How come? How can I fix it? Kittybrewster ☎ 11:42, 13 July 2011 (UTC)

CTRL+F5? Or CTRL+L, followed by CTRL+Z as needed? ¦ Reisio (talk) 14:13, 13 July 2011 (UTC)

Perhaps you are stuck inside a frame? Though, the URL you supplied isn't even a valid URL. Are you sure it isn't the bookmark bar you are seeing? You can hit Ctrl + L to go to the Location Bar (as Mozilla calls it). If you type in a website and hit enter does it still say google/facebook.com ? TheGrimme (talk) 14:20, 13 July 2011 (UTC)

Unreadable external harddrive; missing driver?

Hi, I am currently using an Acer Aspire netbook (can't remember the exact model) with Windows XP SP3. After 3 years of working pretty well, my Trekstor 500gb external hard drive (after looking around the web I think it is a Datastation Maxi G U) decided to go kaput; it will not read, even though the power is on and the light is showing blue. I've tried connecting it both to my own laptop and another (Toshiba something or other running Windows 7 Starter); on my laptop, it is reading as a Sunplus USB2Sata bridge which it most definitely is not, while on the Toshiba it doesn't appear in My Computer at all. On both laptops it is showing "0kb of 0kb remaining", and the other gives an extra message along the lines of No Media Detected. I am currently far, far, far away from where I purchased the drive (15,000 kilometres (9,300 mi) or so) and don't quite trust the local repair shops. Is there a way for me to recover the 300gb or so of data I have on the drive? Would downloading the correct driver help? Where could I download the driver? The manufacturer's website does not have it for download. Crisco 1492 (talk) 17:19, 13 July 2011 (UTC)

You don't need a driver for a USB mass storage device on Windows XP (or anything else that's not ancient); it comes with one. What persuades you that the Trekstor enclosure definately isn't a Sunplus USB2Sata bridge - that's just the kind of thing you would expect such an enclosure to show up as. Some Google searching suggests that many Trekstor mass-storage devices use Sunplus bridges. Most likely either the drive is bad or the enclosure is bad (or maybe just the connection in the enclosure between the bridge and the drive has become loose). The thing to do is to open the enclosure and extract the SATA disk within, and plug that directly into the SATA interface of a desktop PC. If the disk is okay you'll be able to read the data off that way; if the disk has died then you won't. -- Finlay McWalter ☻ Talk 17:39, 13 July 2011 (UTC)

So no matter what I have to see if the "experts" won't botch it and then still charge an arm and a leg? Joy... Hopefully it's only the connection; I don't want to lose some (most, actually) of that data. I guess I'll just put it off until I have the money. Thanks. Crisco 1492 (talk) 17:43, 13 July 2011 (UTC)

Probably. You could try opening the enclosure yourself (with the power off, obviously) and re-seating the sata and power connectors to the drive. I doubt it's that, but you never know. -- Finlay McWalter ☻ Talk 17:53, 13 July 2011 (UTC)

Thanks for the idea, but I have very uncoordinated fingers. Thanks for all the help. Crisco 1492 (talk) 23:45, 13 July 2011 (UTC)

called phone, heard dialup sound

i called a phone number and after a few rings i heard the old dialup sound. does this mean the guy was connceted to the internet by dialup? — Preceding unsigned comment added by Earthumeets9 (talk • contribs) 22:07, 13 July 2011 (UTC)

You called a fax machine. -- Finlay McWalter ☻ Talk 22:09, 13 July 2011 (UTC)

That's most likely, but it could also be a phone modem (dial-up), set to accept incoming calls. It could either be a dedicated line for either of those purposes, or he might just have it set up that way when he's expecting a FAX or incoming dial-up data, and use it as a normal phone the rest of the time. So, you'd better ask him if you have the right phone number, and, if so, when the best time to call is to get an actual ring. StuRat (talk) 18:28, 15 July 2011 (UTC)

Alternatives to connecting to a router which is too far away

What can be done if my router is too far away? Besides that putting my computer nearer it (which is possible, but not what I want), which options do I have to strengthen the signal? 88.9.104.139 (talk) 22:11, 13 July 2011 (UTC)

You can use a wireless repeater, which means it receives the signal and retransmit it to other points in case if the router is too far away. You can look here and here for more information about repeating and wireless repeater. I hope I answered your question. -- Luke ^Talk 22:20, 13 July 2011 (UTC)

Thanks for the prompt answer. And can I also attach an antenna to my computer to broaden its range? — Preceding unsigned comment added by 88.9.104.139 (talk) 22:24, 13 July 2011 (UTC)

Yes, you can use an antenna. A cantenna can be used to broaden your WiFi range. However, it can also pick up other networks in the vicinity. -- Luke ^Talk 22:27, 13 July 2011 (UTC)

I don't know the name for it (I'm sure someone else will), but you can also get a device which uses your power sockets. Its a pair of devices, one plugs into a power socket near your router attached to by an ethernet to the router, and another plugs into a power socket near your computer and cables into that, and the devices have power plug in them too so you don't need extra sockets--Jac16888 ^Talk 22:30, 13 July 2011 (UTC)

I think HomePlugs work like that. --Kateshortforbob _talk 09:57, 14 July 2011 (UTC)

This website has plans on how to make a parabolic reflector to place behind the antenna on the router side, both to increase its effective range and the signal strength in one direction, and to reduce its signal strength in the other direction (that is, the neighbors would have a harder time picking it up). You can apparently make the reflector out of anything metal; a cookie baking tray is suggested on the site, as is tin foil taped to cardboard. Comet Tuttle (talk) 15:18, 14 July 2011 (UTC)