Why we are implementing interfaces ?

Question: Why are we implementing, for example ICloneable or IDisposable. I'm not asking what ICloneable or IDisposable do, but I want to learn what's a good reason to implement these interfaces rather than just writing a method which disposes or clones our objects?
Answer: Using interfaces keeps the use of those pieces of functionality consistent.  That way, when another class wants to / needs to use your class, it can act on it as a cloneable, disposable object without worrying about your particular implementation details.
Comment: I was thinking the same thing sometimes but I wasn't quite sure because there would be something else, But I was kinda right about my thought :) Thank you very much.
Answer: By implementing a well known interface, you can have polymorphism, which enable you to write generic code that can act on any instance of a class that implementes a given interface.
You can check the Wikipedia article on polymorphism for more.
Answer: Because you may want the same code to operate on instances of different classes.  For example, a form cleanup routine wants to iterate over all components and dispose them.  In order for it to do this, it needs to refer to the components through a type: either a common base class or an interface.  Single inheritance means that a common base class isn't always feasible (suppose my form has both a FileStream and a Button -- what common base class could they have that the cleanup routine would access them through?); hence interfaces.
Answer: Adding to more interface wisdom, interfaces can be used as contracts between consumer code and service code. Instead of saying this is object that we will be dealing with, with interfaces the agreement is, this is how the object i return looks. In code, it could be something like:
service code
public IEnumerable<int> GetNumbers(){ return new []{1,2,3,4,5}; }

client code :
var result = serviceProxy.GetNumbers();

Here the service code can change implementation to return any class that satisfies IEnumerable without breaking client code.
Besides all this you have got other applications like IoC DI, Unit Testing, Object Mocking. All this reaping benefits of polymorphic goodness.
Answer: Among other reasons, read about the using block.
Comment: I think it is used for disposing the un-referenced objects.But I wasn't asking that :) well thanks for your time :)
Answer: Phoebus gave a great answer, but to add a bit more.
It forces you to write the methods that are expected for cloning or making something that can be disposed.  If you had to write just the method, would you always include all the necessary methods, or would the signature always be the same?
If there is a new framework, and they add something, to help ensure that the operations are done correctly, by having interfaces then it forces you to implement any new changes, as your application will no longer compile.
Answer: In summary the Interface separates the implementation and defines the structure, and this concept is very useful in cases where you need the implementation to be interchangeable. Apart from that an interface is very useful when the implementation changes frequently.
Interface can be used to define a generic template and then one or more abstract classes to define partial implementations of the interface.
Interfaces just specify the method declaration (implicitly public and abstract) and can contain properties (which are also implicitly public and abstract). Interface definition begins with the keyword interface. An interface like that of an abstract class cannot be instantiated.
Answer: An interface separates what's done from how it's done.  Clients deal with the interface type, without having to know what the implementation class is, because they can rely on the contract it enforces.
This is important for situations that generate dynamic proxies.  Clients need not know that they're dealing with a proxy, which gives you the freedom to inject whatever behavior you need.  It's a common technique for aspect-oriented programming.

Why we are implementing interfaces ?


Usage: "devant" or "en face de"?

Question: I would like to know if there is any difference between "devant" and "en face de". Are there any specific situations in which it would be unusual to use one or another?
Answer: Devant means "in front of", and so relates to location only, whereas en face de means "across from" (meaning there's a third thing to cross to get from one location to the other) or "facing" (meaning the two things being described have a literal or metaphorical "face" that look at each other).

Je suis devant vous dans la file [I'm in front of you in the line — can't use en face de here since people don't face each other in a line]
Je suis assis en face de Paul [I'm sitting across from Paul, eg at a dinner table].
Je suis assis devant Paul [I'm sitting ahead of Paul, eg in a theater]
Je travaille dans l'immeuble en face de la mairie [I work in the building that faces city hall, meaning the two buildings' "faces" are "looking at each other" across a street, square, river, or something like that]
Je vous attends dans le square qui est devant la mairie. [I'm waiting for you in the square in front of city hall; can only use en face de here if there is something that one needs to cross in order to get from city hall to the square.]
Comment: Opposite as a synonym of "across from" is that sense.
Comment: Merci beaucoup!
Answer: People might say that both words are the same, but there is a small difference. Devant means "in front of", whereas en face de means "across from".
Comment: I don't think a lot of people would say both words are "the same" and the difference is not really "small". Read the accepted answer for more details.

Usage: "devant" or "en face de"?


Rpi PIR Motion Sensor HC-SR501 always reads high, why?

Question: I'm trying to use a motion sensor with the Raspberry Pi but despite all the tutorials I followed, the input of the raspberry pi is always high.
Here is my code below.
I used a LED to turn it on when movement is detected but I didn't insert the code to do it yet. I'm trying first to make the motion sensor work.
I thought it was the sensors that didn't work but I have tried with 3 different sensors so it might not be this. I checked all the connection too so it's not the connection. The Raspberry Pi works fine with other projects so it's not the Raspberry Pi. I don't how to solve this. I spent almost 3 days trying to make it work.
Someone help me !
Thank you
Image if my connections
Comment: **DO NOT** post pictures - post text! Without details of WHAT you have used and how it is CONNECTED the Question is meaningless.
Comment: code * (not "Image if my connections", I wrote too fast sorry)
Comment: ok I've made another post with the connections and the written code. I really need help !
Comment: But you can edit your old question here, instead of posting another new question confusing readers. Perhaps you can copy the photo there and pasted it here. By the way, the most important guy, the sensor, is not completely shown there. Is it a HC-SR501?
Comment: https://raspberrypi.stackexchange.com/questions/98371/why-is-pir-motion-sensor-always-on
Comment: Hi @Menelik Nouvellon, Welcome and nice to meet you. Ah, let me see. I quickly read twice your question's three short paragraphs which describe succinctly what you have researched, the problem you encountered, your troubleshooting procedures, and your deduced conclusion, which I think is very reasonable. I have been answering perhaps more than twenty interesting questions like yours in the past two years.  What is  common in those interesting questions is what is reflected behind, the sorrow of problem solving newbies, ... Ah, lunch time. See you later. Cheers.
Answer: Question
How come all my three PIRs are always on?

Answer
Because all of them are bad guys.

Try the smallest guys below. They are very good.

You might like to show your PIR and a schematic, like below.

You might also like to study the datasheet and make a summary for troubleshooting reference.
More details are in Appendix A.  You need to know more details when testing and troubleshooting.

You might notice that the datasheet does not give the output voltage values for motion detect and motion not detected.  What are given are current values IOH, IOL +-10mA, and corresponding VOH, VOL values (Yes, you need a have a basic idea of IOH, IOL, VOH, VOL).  The reason is that PIRs are often placed far far away from Rpi, so outputting currents through a long wire, perhaps 20 meters, and causes a DC voltage drop across a resistance (Note 1) near the Rpi is the usual trick for the PIR application.
If you don't have installed this current sensing resistor, you might have fake positives, I mean High signal, for ever.
I forgot to tell you how to check out the always High PIRs are bad guys.  The trick is to use a rice bowl to cover up the bad guy.  If the bad guy still says something is moving, of course he is lying.

References
(1) Introduction to HC-SR501 A complete step by step tutorial on Introduction to HC-SR501
(2) TaoBao HC-SR501 PIR Sensor Module - ¥3.23
(3) TaoBao DC 12V Water Proof Smart PIR Sensor Module With Switch - ¥12.80
(4) TaoBao AM312 PIR Sensor ¥5.28
(5) AliExpress AM312 DC 2.7 to 12V Mini IR Pyroelectric Infrared PIR Motion Human Sensor Automatic Detector Module  - US$1.29
(6) Pyroelectric Infrared Radial Sensor AM312 (DSP, Schmidtt) Manual - NanYang SenBa
(7) PIR Sensor Description and Technical Details - AdaFruit
(8) PIR Sensor Tutorial - AdaFruit
(9) PIR Human Motion Module 10*8mm 2S delay time SB00322A-1 - Nanyang Senba Optical And Electronic, China
(10) SB312 Passive Infrared Sensor Module for Home Security System
(11) SB612 Human Motion Detector for Smart Toys From Senba Manufacturer
(12) SB412 High Sensitivity Digital PIR Modlue for Light Control Lamp
(13) Senbasensor
(14) Nanyang Senba Optical And Electronic Co., LtdNanyang Senba Optical And Electronic Co., Ltd
(15) How to use HC-SR501 PIR Motion Sensor with Arduino - Benne de Bakker, Maker Guides 2020Jan
(16) HC-SR501 PIR Motion Detect Producat Description
(17) BISS0001 Micro Power PIR Motion Detector IC Datasheet
(18) IR Parts Manual RE200B FL65 S211FL - GloLab
(19) Amazon Panasonic Plastic Pir Sensor (EKMC1603111, 3V~6VDC power, 12m detection range, digital output) - HK$110
(20) Panasonic PIR EKMC1603111, 102°, 12m, 3~6V
enter link description here
(22) HX711 Weigh Scale 1/3
(23) HX711 Weigh Scale 2/3
(24) HX711 Weigh Scale 3/3
(25) Motion - Wikipedia
(26) MotionEye
(27) AlliExpress KonLen PIR motion detector 12V, 110 degrees Detection angle - US$10~40
(28) KeyStone KTS-PIR1-12V-AUX SMART PORT LED PASSIVE INFRARED (PIR) OCCUPANCY SENSOR (0~10V, 20mA Output) - US$30

Appendices
Appendix A - Pyroelectric Infrared Radial Sensor AM312 Specification

Working voltage: DC 2.7-12V;

Delay time: 2 seconds;

Blocking time: 2 seconds;

Triggering method: repeatable

Sensing range: ≤ 100 degrees cone angle, 3-5 meters; (according to the specific lens)

Operating temperature: -20 - +60 °

Features

Anti-interference enhancement, the internal use of digital signal
processing, direct high-low output.

Repeatable triggering mode: If a cat moves in the sensing range during the
delay period, and output is high, output will remain high
until delay time after the cast has left, ie, the sensing module will
automatically delay after detecting an activity of the cat, with the
time of the last activity as the starting point of the delay time.

Appendix B - SB312 Passive Infrared Sensor Module for Home Security System
Update 2020jun02hkt0954

SB312 Passive Infrared Sensor Module for Home Security System
Overview
New Smart PIR Sensor Module with improved digital sensor.
This unit has enhanced delay time adjustments, with an expanded range from 2 seconds to 70 minutes. The unit includes an integral light sensor with adjustable sensitivity, the unit is suitable for outdoor and indoor mounting. Detecting length is also adjustable. The output is a standard TTL output signal, that can be used with a microcontroller or for switching lights, etc.
References
(B1) PIR Human Motion Module 10*8mm 2S delay time SB00322A-1 - Nanyang Senba Optical And Electronic, China
https://www.asmag.com/suppliers/productcontent.aspx?co=senba&id=22978
(B2) SB312 Passive Infrared Sensor Module for Home Security System
https://www.senbasensor.com/products/sb312-passive-infrared-sensor-module-2s.html
(B3) SB612 Human Motion Detector for Smart Toys From Senba Manufacturer
https://www.senbasensor.com/products/sb612-human-motion-detector-for-smart-toys.html
(B4) SB412 High Sensitivity Digital PIR Modlue for Light Control Lamp
https://www.senbasensor.com/products/high-sensitivity-digital-pir-modlue.html
(B5) Senbasensor
https://www.senbasensor.com/
(B6) Nanyang Senba Optical And Electronic Co., LtdNanyang Senba Optical And Electronic Co., Ltd
https://www.asmag.com/senba.co

Appendix C - AM312 Application Schematic

Appendix D - AM312 Setup
This PIR sensor is "plug and play".  This is no adjustments necessary.  Just power and sensor is automatically set up, in two seconds.

Appendix E - HC-SR501 Adjustment Cheat Sheet
Comment: Thank you very much for answering me ! I'll try the AM312 sensor !
Comment: And is it possible to change the block time ?
Comment: No, i'm doing this for me. It's supposed to be a camera that starts filming when an animal (for me it's a reptile) is passing in front of it (that's where the motion sensor is useful). I bought an AM312 motion sensor and it worked better than the HC-SR501. The first sensor I had was good but too much false positives and the second one is not very sensitive (both are AM312 motion sensor). Thank you
Comment: @Menelik Nouvellon. You are welcome. By the way, my PIR knowledge is a bit out of date. So just now I had a quick google to catch up, as summarized in Appendix B. Please feel free to ask me any newbie questions.
Comment: @Menelik Nouvellon, The HS-SR501 always returns High for at least two reasons: (1) They are knockoffs or reject grade pieces, (2) the impatient newbies don't bother to read the friendly user guide and therefore does not set the sensors properly, (say, impatient to wait for 1 minute to let sensor settle down after powering up, turn the adj know blindly, without knowing what they are doing, etc, etc. So if you are waiting for your new toys to arrive, perhaps you can read the manual and patiently try your luck again. References 15~18 are your friends. Good luck. Cheers.
Comment: @Menelik Nouvellon, Just now I set up the AM312 again, just to refresh my memory. As usual, there is no setup necessary, just plug and play, as illustrated in Appendix D. Please let me if you have any AM312 setup problems.
Comment: How nice to hear the good news. Ah, I forgot you are talking about the old guy or the new guy. Pls let me know which manual you are following.
Comment: And I forgot to tell you that you need to read my cheat sheet in Appendix E, to check out if your module is a bad knock off guy, or actually it is a good one. If you digested and "fully" understand my cheat sheet, you might agree that the reason of many newbies complaining that their module is always high are bad stuff.  Actually they are too lazy to read the friendly manual, and therefore do not know how to adjust the ***one jumper, two adj pots***.
Comment: for the AM312 sensor. And also is it possible to change the sensitivity ?
Comment: https://www.senbasensor.com/
Comment: I still have a problem. I have often some false positives (≈ 1 false positive/min) and it's not good for my project because it has to be pretty accurate. Do you have some suggestions? Thank you
Comment: I am hopping among a couple of forums and entertaining more than 10 questions at the same time. So forgive me if I forgot what you are doing.  Could you please update you question, or compile an answer here, detailing all the details, and what have you been trying, so I can refresh my memory. Also please let me know if you are under 16, doing a school project, ... then let me join in your school project website, ... or you own github etc.
Comment: and I forgot if you are using 12V industrial grade stuff, no more Micky Mouse toys? https://www.aliexpress.com/w/wholesale-12v-pir-sensor.html.
Comment: And for entry level supermarket/hospital grade, try this: https://fr.aliexpress.com/item/32890243349.html?spm=a2g0o.productlist.0.0.7eb81379s0UMAQ&algo_pvid=d1ccf58f-3d06-48b5-b00d-9dd7db3328c4&algo_expid=d1ccf58f-3d06-48b5-b00d-9dd7db3328c4-6&btsid=0ab6f82315921832444042305e5838&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_.
Comment: And for hospitals, this is good: Panasonic EKMC1603111.
Comment: Thank you for your clarification. Your project is interesting. I forgot to tell you that beside hopping around a couple of forums, I have been reading Google alert at some 5 or 6 subjects including Rpi, and have also subscribed and  reading "The Code Project Insider Daily Developer News" etc, and I am also DIYing more than 20 home automation projects at the same time, (well, most of them are on and off, stalled and resumed, much like reading 20 books at the same time but which never finished any, ..)
Comment: I need to know more about your background, because I am not interested to share my hobbyist experience with any commercial, or would be start up project sponsors. There are also out there many elite uni grad students doing final projects who would look down hobbyists and would think that their reputation would be damaged if talking to friendly hobbyists. So they multi-post and just hit and run, never bother to reply, ... / to continue, ...
Comment: I also have a home automation project for monitoring gekkos who help to eat mosquitos and cockroaches etc at home. I have been thinking of using Rpi IR camera and HX711 weigh sensor to monitor their behaviour and growth rate, but I have not been using PIR perhaps I might try later. So if you can update your question here as the first PIR selection and setup question. We can move to another new questions, perhaps how to reduce false positives etc. There are too many solutions, such as (1) take moving average, (2) digital filer, etc. / to continue, ...
Comment: Ah times up for my daily morning use of English assignment, see you later. PS,  And before I go, I extract some references from my project log for my English teacher:

(1) Gekko - Wikipedia
https://en.wikipedia.org/wiki/Gekko

(2) https://baike.baidu.com/item/%E5%A3%81%E8%99%8E/1124

(3)  https://ol.mingpao.com/ldy/cultureleisure/culture/20190326/1553538520889/%E5%A3%81%E8%99%8E%E6%96%B7%E5%B0%BE%E7%B5%95%E6%8B%9B-%E5%A5%BD%E5%82%B7%E8%BA%AB%E8%A6%81%E6%85%B3%E4%BD%8F%E7%94%A8, to continue, ...  .
Comment: (4) https://kknews.cc/zh-hk/home/vkvag6q.html

(5) https://skypost.ulifestyle.com.hk/article/2633916/%E3%80%90%E5%A3%81%E8%99%8E%E5%8F%AB%E8%81%B2%E3%80%91%E5%A4%8F%E5%A4%A9%E5%A4%A7%E9%87%8F%E5%9B%9B%E8%85%B3%E8%9B%87%E5%85%A5%E4%BE%B5%E5%82%B3%E5%87%BA%E5%8F%AB%E8%81%B2%20%E5%B0%88%E5%AE%B6%E6%8B%86%E8%A7%A3%E5%A3%81%E8%99%8E%E4%B8%8D%E6%96%B7%E5%8F%AB%E6%9C%89%E5%8E%9F%E5%9B%A0. End of references, cheers.
Comment: The gekkos in my home from time to time make strange big noises, so I googled to find out why.  I once thought of using a gekko voice activated device to start my monitoring system, I also have stainless containers with high slippy walls to trap those little things and take pictures before letting them go. See you later.
Comment: Coming back to your false positive problem, as I said: "There are too many solutions, such as (1) take moving average, (2) digital filer, etc.". Actually (1) and (2) and related. In your case, moving average "absorbs" the abnormal/unlikely measurement is not that appropriate, because it is better to "discard" the too abnormal/almost definitely rubbish measurement. One solution is to use multiple, say two,three or even 10 AM312 digital output PIRs at the same time, and take the "location/device  average". Just brainstorming.  Comments and counter suggestions welcome.
Comment: Last time I gave you the link to senbasesenor.com, hoping that you might find sensors suited to your application. The following may give you an idea: https://www.senbasensor.com/products/digital-pir-sensor/. The sensitivity/delay parameter depends on you application. For example my gekkos are only 2cm to 5cm long, but your crocodiles are 2 feet to 20 feet long, so you need different PIR sensor modules. BTW, if you don't know how to use a multi-meter and don't know Ohm's Law, never heard of moving average, not to mention digital filter, it is hard to give you any suggestions.
Comment: Before I forgot, if you are watching crocodiles 30 feet away, you might like to consider 12V power, 5V DC 20mA output models (Yes, you can of course convert 20mA signal to 3V logic signal for Rpi). Industrial and professional guys usually prefer 20mA signals for less noise interference etc. But those 12V version are usually bulky, as shown in my answer above.
Comment: Coming back to your AM312 PIR false alarm problem. For my gekko video project, I don't use any moving/location average or extreme/abnormal measurement digital filtering methods, because I am using at the same time gekko voice activated, and HX711 weighing sensor, and also Montion/MotionEyte stuff. You may also like to try MotionEye.(1) HX711 Weigh Scale 1/3
https://www.raspberrypi.org/forums/viewtopic.php?p=1395602#p1395211

(2) HX711 Weigh Scale 2/3
https://www.raspberrypi.org/forums/viewtopic.php?f=91&t=233311&p=1428409&hilit=hx711+tlfong01#p1428409, /to continue, ...
Comment: (3) HX711 Weigh Scale 3/3
https://citywidesolicitors.co.uk/bnugrad2/motioneye-raspberry-pi-zero-w.html,

(4) Motion - Wikipedia
https://en.wikipedia.org/wiki/Motion_(surveillance_software),

(5) MotionEye.
https://github.com/ccrisan/motioneye. BTW, my HX711 based weigh sensors can measure in a range of 100g to 10kg, with an accuracy of less than 1%. So I can monitor the growth rate of my baby gekkos and also my microgreens. But your crocodiles are over 500 kg, so my project experience might not be shared. Cheers.
Comment: If your crocodile zoo is outdoor, then you might use a PIR with 12V 20mA output signal which won't be affected by RF interference.  See Refs 27~28 for a catalog and a specific 20mA output signal PIR Example.


What is the Long-Range-Attack in Proof-of-Stake?

Question: What is the Long-Range-Attack in Proof-of-Stake? And how will this vector be mitigated with the Casper Proof-of-Stake implementation?
Answer:
In a naively implemented proof of stake, suppose that there is an attacker with 1% of all coins at or shortly after the genesis block. That attacker then starts their own chain, and starts mining it. Although the attacker will find themselves selected for producing a block only 1% of the time, they can easily produce 100 times as many blocks, and simply create a longer blockchain in that way.

https://blog.ethereum.org/2014/05/15/long-range-attacks-the-serious-problem-with-adaptive-proof-of-work/
Comment: Can you expand slightly? I don't understand how the attack could 'out-pace' the real chain since the main chain would be moving at the same rate (or would it?). Wouldn't the difficulty modifier still require that blocks appear at the same interval?
Answer: From Casper 101:
It's roughly the same mechanism as 51% attack (make a longer chain that rewrites the ledger in the attacker's favor), but instead of starting the attack 6 blocks back, go much further back in the chain's history (i.e. 60,000 blocks). This is a problem for PoS since there's no proof of work (or a time-intensive operation) required to rewrite a very long chain.
This and the nothing at stake problem are solved via ideas from slasher (and its improved variations). The main points are that (1) validators are known, which allow for fault attribution at a validator level and (2) by having "slashing conditions" that strongly disincentivize certain actions, it is possible to mitigate these issues. Again, this example is crucial in understanding the Casper team's view on consensus algorithm design: we can leverage economic mechanism design to a secure distributed system.
Comment: @AndroidDev93 Yes.  The same goes with a normal wallet: if an attacker hacks your wallet, they can steal all of your money.  Keeping your secret key safe is the golden rule no matter if you use PoW or PoS.
Comment: @stackoverflower the PoW miner only has the public key. Not the private key of the wallet. In PoW you never take money out of the wallet. You only put money into the wallet. So, PoW only has the public key. In PoS that doesn't seem to be the case though. You need to be able to slash funds if they respond incorrectly. So, you need to have some sort of private key in the miner.
Comment: If you have something at stake, how do you send the staked coins to the network? Sounds like you need to use the private key or some other key with lesser access. Also, what if nodes get hacked into and a hacker gets the node to send a wrong result to the network? The stake would be slashed and they would lose tons of money?
Comment: @stackoverflower If my PoW miner gets compromised my funds don't get stolen though. My miner only has the public key. In proof of stake, that's not the case though. This sounds like a new vulnerability when comparing PoS to PoW?
Comment: @AndroidDev93 The PoW miner also has a key-pair that is used to receive transaction fees and new bitcoins, though you can regularly move funds out of the miner's wallet to keep the loss low.  With PoS what you can do is to split your funds into multiple miners, and run them in parallel.  This won't use more electricity though, because you can program them so they always make the same decision.


How do I browse all shapes in Visio (2010)

Question: I'm not very familiar with the shapes that are available for me to use. Sometimes I'm looking for a shape but I don't know what it would be called so I can't search for it and I don't know which category it would be in. Please tell me there's some "browse all shapes" option that just shows a huge grid of available shapes and allows me to scroll through it looking for something I want to use.
Answer: This tool may help you: http://viziblr.com/news/2012/3/10/browsing-visio-2010-stencil-shapes-as-a-document.html
It will create an HTML document that shows all the shapes in one or more stencils. So now you can browse the shapes without having to open up all the stencils one by one.
Comment: The html files link http://1drv.ms/1dM6bPX doesn't work.
Comment: And the images on the viziblr website also don't exist, so I suggest this link https://web.archive.org/web/20190928195317/http://viziblr.com/news/2012/3/10/browsing-visio-2010-stencil-shapes-as-a-document.html
Comment: Also, does the tool work with VSSX files?
Answer: Not really.  Unless you make an extensive My Shapes custom listing.  You are going to have to do some searching but it should not be that hard.  Once you have the type of document selected it will give a default setting of shapes to you use and then you simply need to browse over to More Shapes and try to search out what you want.  Give it a little thought and time and you SHOULD be able to figure it out without much trouble.  Worst come to worst, if you don't know what THEY call what you are looking for, Google it how you would say it and more than likely SOMEONE else thinks like you do and noted the term they used instead.
I am not saying this for certain but I am not seeing any way to do it myself.  Good luck if this does not do it for you.


Smoke detectors & backup generators

Question: My home was built in 2014; California code requires hardwired smoke detectors. I also have a 10kW Generac whole-house standby generator. Whenever I lose power, every smoke alarm in the house gets activated...I contacted Kidde to find out why, and the technician responded that hardwired detectors CANNOT be used with a standby generator, because the generator produces voltage spikes that can damage detectors. He said I either need to have the detectors on a circuit not connected to the generator, or use non-hardwired detectors that utilize wi-fi for interconnection. Problem is the 1st solution means the detectors wouldn't operate in a power outage (NOT good!), and the 2nd solution won't meet code, which requires detectors be hardwired. My electrician says he's never heard of hardwired detectors not being able to be used if one has a backup generator, and I haven't been able to find anything about that on the 'Net either. Can anyone shed any light on this or offer suggestions?
Comment: Do your smoke detectors have battery backup? If not, then I'd replace them with ones that do have battery backup since you apparently live in an area prone to power failures, and even if your generator can power the smoke alarms, you probably don't want to count on it.
Comment: Are the smoke alarms actually going off, or are they chirping (low battery/trouble)?
Answer: California also requires battery backup for hardwired detectors.  So you could separate that circuit from the generator safely.
Most consumer level power generators do not produce the same quality of power as the power company.  Total harmonic distortion (THD) may be much higher.  Generac is a good company, but they don't specify a THD on the data sheet for  their 11/10kW Guardian Series generators.
I find that regular loss of power sets off hardwired detectors.  I just consider it a power failure alarm and move on.  The switchover from the power company to the backup generator will never be 100% smooth at this price level.
Answer: This is certainly a new one for me also. I'm not sure this is a problem with the smoke detector or the manufacturer's technical support. Let's start with his statement of the generator spiking. Technically a 10 kw generator can only spike to 10 kw and I doubt the governor would let it get that high. There is more of a chance you get a sag (low voltage) or a stall (loss of hertz) than a spike. Also if what he told you is true I would think that that would be listed in a tech report somewhere. What I am trying to figure out is how would any of this effect the electronics of a smoke detector?
The only thing I can think of is maybe some of the exhaust is getting into the house and setting off the detector.
I would suggest contacting a the generators tech support, or a competitor's tech support and repeat what the manufacturer's tech support said and see what they have to say. Also if you contact the manufacturer's tech support again I would ask for an engineer and see if he could give me something better than what you were originally told or ask for some documentation. Because if what the tech has told you is true, I would say they have a very bad problem.
Hope this helps.
Answer: I've never heard about the "no generator" thing, but I do know that low batteries will cause this dilemna. Replace all the batteries, in all the detectors.

Smoke detectors & backup generators


Can somebody identify this tea?

Question: I was eating at my local Denny's and when you ask for tea, they give you some hot water and two of the below tea bags. On the menu it says "Hot Tea / Herbal Tea" but the tea bags only say Lipton and don't say what kind. I am hoping to identify what type of Lipton tea this is. I know the inside has a number on the bottom which didn't help me in Google.
Answer: The webadress "www.ufs.com" and the text "This unit not labeled for retail sale" tell you that this is the tea mix Unilever delivers to restaurants, senior homes etc. The rainforest alliance logo is used for coffee and black tea, so it's not herbal tea. (That the menu lists both, only means both are available, typically for the same price; without qualifier a server will always assume "tea" = "black tea".)
As this paper wrapper does not give details, you could ask your server (tip generously...!) for package details or check the ufs website. My gut feeling is that it's the standard Lipton black tea:

... or at least a very similar blend.
Comment: Stephie - While this is clearly a foodservice item, not being labeled for retail sale does not mean that a product can't be sold at retail. It means that the individual unit is not for retail sale, so you would have to buy it in a package of "X" number of units. This same wording is often found on retail items that contain more than one unit as the units are not meant to be sold individually.
Comment: I finally was able to strike a conversation with a server who brought the entire box out to show me. It was Lipton 100% Natural America's Favorite Tea (Serve Hot or Iced) 100 Tea Bags as you show above. I noticed that the tea didn't taste the same at first because I believe that my tea water is actually TOO hot. Once it cooled down a little bit it started tasting the same.
Answer: Lipton brands it's tea as "Orange Pekoe", which this essentially means it's black tea from India or Sri Lanka. Black tea has caffeine in it, Lipton averages at about 40mg per cup, which is pretty moderate compared to coffee, but is not caffeine free like some herbal teas.
Comment: From Google Images, when I type in Lipton Black Tea Bags, the packaging is exactly the same when other variants have different labels. Thank you for pointing out black tea as I thought I Googled that before.

Can somebody identify this tea?


Why do we not write "Arrêtez-vous" in "Arrêtez de manger toutes les glaces"?

Question: For "arrêtez", why isn't this "arrêtez-vous"? I have a feeling the "you" is implied, but for other sentences that give an authoritative order, "-toi" or "-vous" is added in front of the verb (like "Asseyez-vous sur cette chaise!" meaning  "Sit down on this chair!"), so why not in this case?
Answer: For discussion on arrêter in particular, refer to Reflexive form of "arrêter" for habits
In your example of Asseyez-vous, vous is necessary because the imperative here is derived from s'asseoir, a reflexive verb, and a reflexive pronoun must be retained. (In the case of tu, it is changed to toi in certain situations.)
In general, however, it is not true that clauses that "give an authoritative order" (i.e. that are in the imperative) necessarily have a reflexive pronoun attached to the verb. If the verb in the imperative form is not reflexive, there will be no reflexive pronoun. (This may be more obvious if you rewrite these imperative clauses as declarative clauses.) For example:

Sauvez-moi de la mort qui m'attend ! (Save me from the death that awaits me!) Here, sauver is not used reflexively, and the clause is essentially the imperative form of Vous me sauvez …
Épargnez votre enfant ! (Spare your child!) Again, here, épargner is not used reflexively, and the clause is the imperative form of Vous épargnez votre enfant.
Comment: Somewhat of an incomplete answer, but my comment got too long and I need to go back to sleep. Hopefully I'll find something more satisfying with regards to *arrêter* later, or someone else will supplement there.
Comment: Have a good nap! Pleasant dreams!
Comment: This argument of yours to the effect of justifying the non-necessity of a pronoun is  obscure, not really making a point, that's what it seems to me anyway. The simple matter of it is that if the verb is not reflexive, adding a pronoun referring to the subject makes sense only if the "cod" or "coi" of the verb is the object or person represented by the subject; otherwise you introduce ambiguous notions, and construct a sentence that is incorrect from the point of view of syntax.
Comment: @LPH I interpreted the question as primarily about why not all imperative verbs are followed by a pronoun, so I'd wanted to give 1-2 different conceptualisations of my examples to try to make the logic of it more obvious (to me anyway).
Comment: I see, the question *should* be taken as more essentially a comparison with all imperatives, as you do. According to what you say the rewriting makes it more obvious, but then in what does the correspondence prove anything since you declare at the outset that it is not true if the verb is not reflexive. Knowing that there is the declarative form "Vous me sauvez…" does not tell you that in the transformation a change shouldn't take place, such as adding a pronoun. Let's take the transformation "La maison est loin." → "La maison est-elle loin?". You do have an intrusive pronoun here.
Answer: There are two forms of the verb to take into account, the transitive (arrêter qqc) and the pronominal (s'arrêter). Both can be constructed with a completing infinitive introduced by "de" (ref.1, ref.2, ref.3).
You can see from those ngrams that the two forms exist for the following verbs: "travailler", "fumer", boire". The meaning is the same. However, usage has it that you don't say "Arrêtez-vous de fumer." (at least not much, if at all) and only "Arrêtez de fumer is found." (ref.4). Similarly, for "manger" only the transitive form is used ("Arrête de manger.", Arrête-toi de manger.",  (ref.5)). Neither "Arrêtez-vous de manger." nor "Arrêtez de manger." are found and in the latter case this is understandable as le lack of familarity with the persons talked to proscribes formal injonctions; however "Arrêtez de manger." is correct.
When you are dealing with the verb "asseoir" or rather "s'asseoir" in the context you mention the big difference is that you don't have a choice, there is just one form, "s'asseoir".


How did Commander Erwin know that the spy/traitor(s) would be within the 104th training squad?

Question: During the female titan arc, how did Erwin specifically know that the traitor would be from the 104th training squad?
Answer: From a well established Tumblr blog post:

After the death of Sawney and Bean, Erwin then was able to narrow down the list of suspects, as only a soldier was able to kill the titans with 3DMG. Because of this, he went around asking cryptic questions to try to weed out liars and traitors, making people second guess themselves.
Then comes the night of the ceremony where the cadets join the Survey Corp. That night, Erwin instructed Levi to take Eren out on a ride to recon the area. Why exactly would he do this? It's clear it wasn't just a normal exercise, as Levi was rushing Eren and seemed frustrated and stressed. This was Erwin's way of narrowing down the suspects. By having Eren leave and the ceremony on the same night, he could deduct that if the enemy did not attack Eren or at least show up to the castle to kidnap him when it would have been strategically best to do so, then it must mean that they were otherwise preoccupied somewhere else. Where else? The ceremony. If someone was missing from the ceremony, it would be suspicious and draw attention to them. So this narrowed down the suspects to the 104th Trainee Corp.
Answer: Captain Erwin is known for his cunning. He is always steps ahead of the situation:

 1. Expecting spies/traitors in a war is common
 2. The appearance of the Colossal Titan and the Armored Titan seemed more than just "random". They always appeared out of nowhere, but perfectly timed - i.e. when the Coordinate power was lost from the bloodline, when the Colossal Titan appeared in front of Eren after the survey corps success etc.
 3. During the battle of the Trost District, they see Marco dead on the floor where half of his body is eaten. However, it was pointed out that his maneuver gear was missing, leading to think that someone took it. But the majority (or only) of the survivors were members of the 104th squad. Later, when Sawney and Bean were killed, they did a thorough check on all members' gears but all were fine because Annie (the killer) used Marco's gear
Answer: And he specifically mentioned Eren in his speech to the 104th Trainee Corps, plus he mentioned his basement having the secret behind the Titans
He suspected it must have been one of those who saw Eren at Trost, in the 104th
I'm guessing it was helping set the bait for the traitor, and spook them


How does an octobox differ from a rectangular softbox?

Question: Octoboxes and more-typical rectangular softboxes appear to have similar structure and function. How do they differ, and when would you use one over the other?
Answer: An octabox will give you nice round catchlights and produce generally more natural looking highlights and reflections. The straight edge of a softbox often sticks out when shooting with reflective surfaces more than a more organic curve or circle.
On the other hand softboxes are easier to mask and gobo due to the straight edges, and more suitable to certain technical lighting styles (e.g. for product photography where you want lights parallel to certain surfaces or at an angle to 'feather' the light). They are often cheaper, and easier to set up and tear down.
You can't go too far wrong with either, I prefer boxes in small sizes for simplicity / control and octas in large sizes for a natural light look and inconspicuous reflections.
Comment: Can you tell me what kind of desk lamp would do for lighting of softbox? I just think I can leverage one at my house instead of buying expensive one and big.
Comment: @Boris_yo unless you are shooting in complete darkness, with the lamp as the only source of light then a desk lamp will be nowhere near bright enough to light up most softboxes.
Comment: Your point is shooting in darkness is the only way to have desk lamp light up softbox?
Comment: You can put a desk lamp in a softbox, bus as I stated it's not going to be bright enough to be much use, unless your ambient light is very low.
Comment: What if I bought 2 desk lamps? And what temperature of bulb I need for this? I assume day or cold? otherwise I feel I will need to use flashlight as well as I have a flexible stand for it. The last case would be to order professional photography lighting lamp...
Answer: Octaboxes tend to focus the light a bit more than square or rectangular softboxes. Some fashion and portrait photographers favor them for several reasons:

More light out of smaller box because of focusing effect
Interesting catchlights in the eyes. If you look at a lot of portraits, you can start to recognize the ones shot with beauty dishes, octabanks, and softboxes by the catchlights

In terms of the "more light" point I brought up, the fact is you can only get so many lumens out of a give light at a given power. However, the diffusion of that light absorbs some of the light, reducing the amount that reaches the subject. The more narrowly the modifier focuses (think parabolic reflector), the more light appears to fall on the subject. In this regard, my opinion is that octabanks are very useful.
You'll also find some really big octabanks that are useful for lighting wide or tall scenes evenly.
I would typically use a softbox for less-than-perfect complexions, older (i.e. > 35 years) people, and products where shadows are to be minimized. Octabank is a mod I favor for younger models who have good complexion. I don't use them for product.


Is there a way of getting a super magical chest or a legendary in Clash Royale?

Question: I am in Royale Arena and I still can't obtain a legendary card. All I got is this hut spawner and second of all, I got too many epics and people keep beating me with those legendary cards.
Comment: One [source](http://clashroyalearena.com/guides/get-legendary-cards) suggests: "I've done some research by compiling data from over 100 super magical chest openings from players in Arena 9 from the recent update, and I've found that the chances of obtaining 1 of the 5 Legendary cards from a single **Super Magical Chest is about 40%**"  When you say you want to know the percentage, do you mean across all possible ways to obtain one?
Comment: You've accepted an answer, and let a bounty time out on a different answer. Now you've put up another bounty with a nonsensical description. What exactly are you looking for?
Comment: I am not understanding why an open bounty was offered, then applied to an old answer that was not updated despite new answers (I am not trying to farm reputation; I just don't understand your motive behind offering this bounty, especially after there has been an accepted answer, and the answer that you gave the bounty to [twice!] is not your accepted answer.)
Answer: There are many ways to obtain Super Magical Chest and legendaries. However, I'm assuming that you do not wish to pay a lot of money on this game, so I didn't include the option of purchasing Legendary King's chest. However, Legendary chests are a feasible option, so that's included below.

Attempt to obtain the chest from battle.
You are guaranteed a Super Magical Chest, Legendary chest, and Epic chest every 500 chests. That means you have a 0.40% chance of obtaining a super magical/legendary chest from winning a battle. If you want to know EXACTLY when your Super Magical and/or Legendary chest will arrive, try royaleapi.com. Conditions: Arena 2 or above to get a Super Magical chest, Arena 7 or above for legendary chest
Purchase legendaries from the shop with gold
Occasionally, legendaries will appear in the shop, purchasable for 40 000 gold. This method is best if you want a specific legendary. Conditions: Arena 10 or above for legendaries to appear in the shop
Wait for the Legendary Chest Offer to appear in the shop
Occasionally, a Legendary chest will appear in the shop and can be purchased for 500 gems. This chest unlocks immediately and is limited to 1 per offer. (The offer will appear multiple times, however, usually every few weeks.) This chest guarantees 1 Legendary from any arena, but it's random, so it's best if you don't care what legendary you get. Conditions: Arena 4 or above (unverified) to receive chest offer
Try and get it from regular chests. Conditions: Arena 4 or above
Check out the chances of getting a legendary of any chest here: https://pixelcrux.com/Clash_Royale/Card_Chance/Calculator
Obtain Super Magical, Legendary, and Legendary King's chests from Quests
With the latest update (10/9/2017), chests are now obtainable as a Points reward for completing quests, and can reward ANY chest obtainable from battle (except Silver), as shown in the Quests screen.

Sources:

http://clashroyale.wikia.com/wiki/Chests - card rarity, chest cycles, arena requirements for special chests
I purchased 2 legendaries with gold.
Personal experience - purchased legendary chest on Arenas 6, 8, 10, 11
Comment: +1, this is better than the accepted answer IMO
Comment: Thanks! Even though I am in arena 10, this suggestion was helpful.
Answer: There are only a few ways to get them, but it's possible. The following are based on being in Arena 9:

Opening Super Magical Chests - Super magical chests are the highest quality chest in Clash Royale. They can be obtained by buying them for 4600 gems in the store, or getting a very lucky drop at the end of a battle.
Buying them from the shop - While rare, they will sometimes appear in the shop and costs 40,000 gold. This is actually a much better deal than the Super Magical chests because 40,000 gold is about 2,000 gems.

Other than that, there's not much to do. There is a better chance to get a Super magical chest drop as the higher your rank is, so just keep trying to climb and refine your deck to the meta.
Comment: You do know the OP mentioned the newer Legendary ***chest*** right?
Comment: Nope, I am trying to get a legendary card by luck or probably for that free to play player such as myself trying to get a legendary card although I am not that rich.
Answer: Since you have put up a bounty and indicated that you are looking for the exact percentages of getting a legendary card drop, the formula for this can be found here:

% Chance = ((Cards in Chest * # Legendary)/# Commons)/Legendary Factor

On the page, there are more detailed breakdowns of the legendary chance based on Arena level and type of chest, which I believe is what you are looking for.
Comment: Nice! I understand the odds!
Answer: While Legendary cards are technically obtainable from any chest beside the epic chest, they are fairly rare. Super magical chests, which drop randomly in 500 chests won from battle, have about a 50% legendary drop rate. The legendary chest, which has the same odds of a super magic chest from dropping, contains one guaranteed legendary. And, legendary cards appear in the shop if you are in legendary arena every so often. Watch this video from Orange Juice.
Comment: Takes about an entire year and it used to be 1/1000 and now it's 1/500
Answer: I only have the log, the lava hound and the inferno dragon. I just got the inferno dragon from a free chest which made me flip out. I got the lava hound from buying the Royal Arena bundle and I spent the ready of those gems on the legendary chest that appeared the next day. You can also get them from spending gems when they are released in the shop.
Answer: My first Legendary was EWiz from a clan chest at arena 7 (about 7% chance at 10/10) Next week, I got Lava Hound from another 10/10 clan chest. Join a clan with good reputation and hope for the best. Also, You always pull a Legendary chest as first chest in third cycle. I wish you good luck.
Comment: That's cool! Legendaries are common for me because of Hog Mountain.
Answer: I did not get any legendary , but I was still in jungle Adena. But one day i opened the clan chest I got log and next week got princess, and next week got best legendary ewiz
Comment: Cool! Even though I have too many legendaries, I am just testing them.
Answer: Getting a legendary or magical chest depends on chest cycle . legendary chests comes in around once in 500 cheat once you  have unlocked legendary cards after reaching certain arena I only got one legendary chest and got inferno dragon  and got 3 legendary cards from other chests .I think there are some apps that keep track of this cycle


How to save webpage as a image file using PHP?

Question: I want to save webpage as image file or i want to take snapshot of an webpage using PHP. Just like firefox extension Fireshot doing.
Comment: or this one http://stackoverflow.com/questions/686858 or http://stackoverflow.com/questions/713938 or http://stackoverflow.com/questions/1952570 or http://stackoverflow.com/questions/1340917 or http://stackoverflow.com/questions/65078 or http://stackoverflow.com/questions/834445 or http://stackoverflow.com/questions/3022338 or http://stackoverflow.com/questions/1077970
Comment: check out this discussion: http://stackoverflow.com/questions/757675/website-screenshots-using-php
Answer: Check out http://browsershots.org/ and Webkit2Png
Answer: You'll need to render the page with something. If you really want to only use php, i suggest you HTMLTOPS, wich render the page and output it in a ps file (ghostscript), then, convert it in a .jpg, .png, .pdf.. can be little slower with complex pages (and dont support all the CSS).
Else, you can use wkhtmltopdf to output a html page in pdf, jpg, whaterver.. Accept CSS2.0, use the webkit (safari's wrapper) to render the page.. so should be fine. You have to install it on your server, as well..
Source: Website screenshots using PHP
Answer: Like others have said, it would be difficult to do in PHP alone. However, there is an easy-to-use cross-platform tool called CutyCapt that does exactly what you need. The best part about this tool is that it's stand-alone and doesn't depend on anything else.
Answer: You cannot do this with pure PHP, try forking a browser like Mozilla with headless mode and let it handles taking snapshot of the page.


Files from my camera are very large: does this present any problem?

Question: I have a Nikon D3200 camera.  When it takes pictures in high resolution, sizes can be up to 6016×4000 pixels. Is there any problem (apart from big files) having the pictures at this resolution? Would it pose a problem when viewing unless you zoom in?
Should I resize them to a smaller size? If so, which ones are recommended?
Comment: It's unclear what is being asked here.  Do you have a problem with handling 24mp images or is there some other reason you feel 24mp images from a 24mp camera would potentially be a problem?
Answer: Rule of thumb: you never have enough resolution.
You should always keep the original files that come out of the camera the way they are.
If you need smaller or otherwise modified versions, create copies of the originals and apply those modifications to the copies. If you shoot RAW (which you should), this is usually the case, as the RAW files aren't image files anyway.
If you want to display the images n a website for example, you do not need that many pixels, because nobody has a screen this big. For that purpose, create smaller versions of your originals for web publishing. (this also reduces the file size that you mention, which is beneficial on the web, too)
Comment: +1. I think worth specifically noting the transfer time for full-resolution pictures. While you should keep the originals, it might be useful to _also_ produce a smaller set, at least of the ones you want to share online.
Comment: Thanks! I was not sure whether being to big would mean the quality would decrease when fitting such a big image in a small screen.. For example in my camera´s screen if I do not zoom in, the image is not seen very well.. It is probably an extreme case though. Thank you again.
Answer: If you want them to be smaller, you can lower the resolution.
The setting is where you see "Raw+F" on this image, you could change yours to "Medium".
http://www.gadgetguy.com.au/cms/wp-content/uploads/nikon-d3300-review-2014-06-08-450x230.jpg


Left-handed persons and usability

Question: I have never seen any UI that depends on what hand a person prefers.
I have never seen any options or profile settings for left-handled persons.
Maybe it is a strange question, but I have to ask it.
Is it common to skip these users? Maybe it is not so important for left-handed persons.
In my opinion, I would like when some things (often used) are placed from the right hand (menu, card, shortcuts)
Comment: There are now a number of phone applications that do have a "handedness" preference, and swap controls to accomodate. Example: Twitterrific.
Answer: Somewhat related to Dan Barak's answer, I find it worth noting, that a touchscreen device - especially a mobile, one-hand operated touchscreen device - is not always operated by means of the user's dominant hand (Silfverberg et al. 2000). Approximately 93% of the population are right-handed.
Furthermore, there is a certain physical dimension not to be overlooked: Several studies (Perry & Hourcade 2008; Karlson et al. 2006; Parhi et al. 2006) have found that users prefer to interact near the center of the touchscreen, thus avoiding extreme flexion and extension of the thumb. (And to avoid total occlusion, one suspects.)

References:
Karlson, A. K., B. B. Bederson & J.L. Contreras-Vidal (2006). "Studies in One-Handed Mobile Design: Habit, Desire and Agility", Tech Report HCIL-2006-02, Computer Science Dept., University of Maryland
Parhi, P., A. K. Karlson & B. B. Bederson (2006). "Target Size Study for Thumb Use on Small Touchscreen Devices", Proceedings of the 8th Conference on Human-Computer Interaction with Mobile Devices and Services, vol. 159, September, 2006, pp. 203-10
Perry, K. B. & J. P. Hourcade (2008). "Evaluating One Handed Thumb Tapping on Mobile Touchscreen Devices", Proceedings of Graphics Interface, vol. 322, May, 2008, pp. 57-64
Silfverberg, M., I. S. MacKenzie & P. Korhonen (2000). "Predicting Text Entry Speed on Mobile Phones", Proceedings of the SIGCHI Conference on Human Factors in Computing Systems, April 2000, pp. 9-16
Comment: I am aware that this is not an answer *per se*. It is, however, too long to be a comment on @Dan Barak's answer.
Comment: I think this is an excellent point. After reading the question, I started thinking that myself--from what I recall offhand, I tend to use both hands equally on my various touch devices...often due to touch UIs not necessarily needing to be pixel-perfect accurate.
Answer: Only physical devices should be affected by whether the person using them is right handed or left handed, for example mice.
A touch screen is one area where you might want to consider such things, as you have considerations of the person's hand physically blocking the view.
When relating to regular site and applications, the right (pun intended) question to ask is what is the user's preference, OR take into consideration the orientation of the person's native language.
For example, most languages are written left to right, hence your UI should take into account that the user will view the elements on the screen in that order (and top to bottom).
If you do allow customizations, it still doesn't depend on whether the person uses their right or left hand. For example, a friend of mine uses Windows' task bar (where the "start" , quick launch and minimized applications are) docked left, instead of the regular bottom.
It makes more sense to ask what the user's preference is, i.e. do you prefer the viewing pane on the right or on the left, rather than asking them about being left or right handed and making UI assumptions based on that.
Comment: take into account as well that a lot of left handed people have found workarounds for things and are uncomfortable using special functionality designed for them (often by right handed people who just mirror everything and call it left handed). I use a mouse with right handed button mapping in my left hand for example, have done so for over 20 years, using a mouse with left handed button mapping is nigh impossible for me now.
Answer: My wife is left handed but she uses the mouse in her right hand. So do most of the left handed people I know.
Most computers are set up with the mouse on the right so instead of having to switch every time left handed people just get used to it.
We don't make left handed door knobs, or left handed stick shifts.
(As a bonus, left handed people are forced to be more ambidextrous and according to many studies this make them more creative)
Comment: +1 It seems very sad (door knobs, stick shifts)...like a discrimination. really, how many things we do not notice. we are just adaptees! ;)
Comment: For another single data point: I'm left-handed, and I do mouse left, buttons *not* swapped, middle finger for left click, index finger for wheel, middle and right click.
Comment: These days we have seen devices designed for left handed users as well, like left-handed mouse, stylus, etc.
Comment: +1 for "...according to many studies this make them more creative" :) Good case for: Dark UX done right!  or UX for good health!! ;)
Answer: Being right or left handed doesn't have much bearing on how you browse the web.  I am right handed but I find it perfectly comfortable to start on the left of the screen and work my way right.  The same would go for someone who is left handed.  What matters more is not whether you move the mouse with the left or right hand, but what direction you read from.  Westerners generally read left to right so that's what we give them.
Answer: Another important aspect is mental models. Like Sruly pointed out, many left handed people work many things right handed way. Surely, that develops a mental model.
When you think of UI, there are a few things which change based on what is the prominent hand for a user. One example is of keyboards, where in the traditional key layout, the thumb travel to hit enter or backspace for a left-handed person is significantly more. In these cases, you do offer options to flip the layout.
In many other cases, user get used to of the layout, and as other answer pointed out, somewhat ambidextrous people use interfaces as a right hand person would too. As their mental models are set to expect things like a right handed person would expect.

Left-handed persons and usability


In the end of Sicario, why does the cop say "Medellin" while the gun was pointed at him?

Question: In Sicario, the word "Medellin" really confused me. I believe it's Alejandro's (Del Torro) last name, and Matt Graver (Brolin) says that it refers to a particular era in Mexico (I forgot the exact words) when Kate Macer (Blunt) asks what it means. Then in the end when Alejandro is pointing his gun at the cop after he exits the tunnel being raided, the cop quietly says "Medellin...". Is he saying Alejandro's name? If so how did he know who it was? If that's his last name why does IMDB only refer to him as Alejandro? If the word refers to an era, why would the cop just muter that to himself?
Answer: Medellín refers to the Medellín Cartel, which was a Colombian drug cartel that operated from 1972-1993 and was probably the largest ever to have existed.
I don't have all the answers, but here's the evidence from the movie:
After the meeting with the US Marshals:

Macer: "Where were you sent from?"
  Alejandro: "Cartagena" (a city in Colombia)

Alejandro also says he was a prosecutor, working for Mexico.
During the interrogation of Guillermo:

Graver: "Ah Alejandro, I think he remembers you"
      ...
      Alejandro: "Now you'll learn what's hell in Yankee land"
      Guillermo: "No Medellín"

After the tunnel firefight:

Silvio to Alejandro: "Medellín?"

Graver and Macer after the firefight:

Macer: "What is Medellín?"
     Graver: "Medellín refers to a time. When one group controlled every aspect of the drug trade. Providing a measure of order that we could control. What you saw there was Alejandro working toward returning that order"
     Macer: "Alejandro works for the fucking Colombian cartel"
     Graver: "Alejandro works for anyone who will point him toward the people who made him"

So, Graver here is saying that Alejandro does not work for the Colombian cartel (though may have earlier in order to get closer to the Alarcon cartel).
According to Wikipedia, Alejandro's surname is Gillick.
Answer: Medellin is the rivaling cartel, which the US sides with in the movie.
Alejandro works for them, taking out the competition on behalf of the US.
Comment: How did you pick up on this?
Comment: Alejandro wants revenge for his wife. That is why he kills the entire family before shooting the actual boss at the end. Because of that loss he swapped sides to a diffrent cartel, which can be deducted has to be the other big player (Medellin). At some point during the movie Josh Brolins character says that the Medellin cartel is something that's controllable by the U.S. government, where as the Mexican cartels refuse to limit their violence and scope, so they're attempting to install a more U.S. friendly drug cartel.
Comment: Okay one last question. Any thoughts on how the cop would now that he worked for Medellin?
Comment: alot of people are interpreting that family in a certain way:

https://www.reddit.com/r/movies/comments/3n6gmc/official_discussion_sicario_spoilers/cvly811

if you read that comment it sums up how his entire family plays into the movie, eventho they have very little dialogue
Comment: Hmmmm. That's interesting.


Canadian citizen with British passport visiting USA

Question: I am a Canadian citizen with a British Passport and I live in Canada and I am planning on traveling by car to Buffalo USA and then boarding a plane to the West coast for a holiday. Will I have any problems crossing the border?
Comment: If you are a Canadian citizen with dual citizenship travelling into Canada by air, you must present a Canadian passport at the border: http://www.cic.gc.ca/english/visit/dual-canadian-citizens.asp  As of now, that does not apply to land borders.
Answer: No, you won't.
Or at least, not more than any other British citizen crossing the border, which is to say you won't be denied entry but it will take you longer than a Canadian passport holder.
At the border you will be treated as a British Citizen, which means fingerprinting, a greater degree of scrutiny and some forms to fill in, and a payment. With a Canadian passport you would probably be waved through after some straightforward questions. I've never tried presenting my Canadian citizenship card as well as a British passport, but you might try that.
Not an answer, but I strongly recommend getting a Canadian passport. It stops you having to put up with these inconveniences, and allows you to apply for a NEXUS or similar card which will speed you through the whole process.
Answer: Given that you are a dual citizen (British and Canadian) you can get a Canadian Passport at one of the Passport Canada Offices, which there are many around Toronto in 24 hours for C$110 and then as a Canadian citizen travel to the United States with no issues of Visas, ESTAs, VWPs or similar.
Comment: That's $110 in addition to the passport fee.
Answer: While the UK is a Visa Waiver country, the VWP status has nearly zero advantage for crossing into the US by land, because of the need to park your car, get out, line up, and then fill out an I-94 form (which you also need to pay for). On a busy day, that can easily add an hour or two to your border wait time (especially during an era of currency parity when every Tom, Dick, and Harry is making a beeline for cheaper shopping).
Canadian passport holders only need to show their passports at the booth and then they're on their way - no need to get out of the car.
Get your Canadian passport - it's well worth the fee. Also, I believe Canadian citizens are required to use their Canadian passports to enter and leave Canada, even if they hold other citizenships. The law isn't really enforced, but better safe than sorry.
Comment: "which you also need to pay for": $6 is a lot less than $160.


Is the tank scene in the A-Team physically possible?

Question: The scene where the A-Team is in the tank and its falling from the air, they fire the canon and it stops from falling for a moment before falling again. Is this possible from a Physics point of view?
Comment: This looks like a good question for Randall Munroe's [What If?](https://what-if.xkcd.com/).
Comment: While this seems to be absolute crap (regarding physical reality, of course, not regarding the A-Team, in the movie this scene was just amazing), I heard that someone checked if this is possible and came to the conclusion that it *might* work. But I have absolutely no sources on this currently. That being said, dropping a tank on parachutes is not that uncommon or impossible in the first place.
Comment: This is really a question for physics.se
Comment: This has already been posted to physics se and answered. But I didn't realise it was still here. Should I take it down?
Comment: this has already been answered http://physics.stackexchange.com/questions/134943/is-this-scene-from-the-a-team-explainable-by-physics
Comment: Well, I mean, there's this, if it helps: https://youtu.be/oZIzreiseMk?list=PLAbMhAYRuCUj-KQESSDcNvZe204qJyE2C
Answer: Let's do some sums.  I can't find specs for the main gun, but a similar British Army 105mm light gun fires shells weighing 15.1kg at 709m/s.  Using 1/2mv^2, that's 3.80MJ.  Let's assume all of the energy from the firing went into the projectile when the tank was on solid ground, because that's the worst case - anything else would improve our chances of stopping the tank.  Since the tank and projectile are now free-floating, half the force (and hence half the kinetic energy) goes to the tank.
The lightest M8 tank was 19.25 tons, which is 17,463kg.  If the tank was falling at 14.7m/s (53km/h), one shell would stop it completely.  From there on, doubling the speed needs four times the shells - so 29.5m/s needs four shells, 59m/s needs eight shells, and so on.
That's discounting acceleration from gravity between shots, of course.  The main gun manages 12 rounds a minute, which is 5s between shots.  If the tank is free-falling, that's 9.8m/s/s acceleration, which clocks up 49m/s between shots.  So even if they weren't moving when they started firing, they couldn't keep the tank up.  It seems unlikely that the single remaining chute (after the Reapers had shot the rest) would slow the tank enough that the gun could even keep up with gravity, never mind bring the speed down enough for a survivable impact on the lake.
Answer: The physics at work here are compression waves and terminal velocity.
Think of a large speaker cabinet.  If you stand up a piece of paper a few feet away and put the volume of your stereo all the way up, the paper will be blown over.  Much like Sonar, the compression waves move air toward an object.
Now, to stop a steel tank, those waves would have to be incredibly powerful.  It's not likely that compression waves from a tank cannon could generate enough force to stop or even slow down an object that likely weighs a couple tons travelling at terminal velocity.
Comment: @VedranŠego No. You'll slow down the tank a tiny bit, but only by a marginal amount. You obviously heard about *actio = reactio*, so *E_projectile = E_recoil* applies, but don't forget the massive mass difference between the tank and the shell. If you see a tank shooting and there's visible recoil (like the tank shaking), then this is really just due to the fact that this recoil doesn't have to directly work against the tank's own weight.
Comment: No, the only relevant physics is recoil.  @Mario is wrong about the mass difference.  Recoil has two factors: one is mass, and the other is the acceleration of the projectile (F=ma), and that force is directly applied to the tank which experiences F=ma in the opposite direction.  Terminal velocity would be relevant if the tank reached it, but they're trying to slow it down so it isn't.
Comment: What about recoil?
Comment: I'm not a physicist, but I'm pretty sure this is incorrect. As Graham states, it's recoil at work. The physics here: http://www.bsharp.org/physics/recoil
Comment: Also, I don't believe the tank ever hits terminal velocity as it has parachutes...it just reaches a speed faster than the human body would appreciate upon landing.
Answer: Tank guns have the technology to compensate the Recoil of the fired shoot.
This Wiki article is about recoil and mordern ways to compensate it.
And this article is about the Muzzle brake - also to minimize the recoil.
Both technics are straight against the fact that a fallen tank can be slowed down by shooting its gun. It would only start to spin around.
The only other thing I could think of that could (very unlikely) help them is the therorem of self lifting bodies.
But not only therefor the Tank must have gotten rid of the parachute, it also needed to get a bit more round on its edges.
Comment: This xkcd "what if" discusses the lift created by various machine guns and might be applicable reading material. https://what-if.xkcd.com/21/
Comment: Recoil and compression waves are not the same.  When the projectile is fired, it still pushes air towards the object.
Comment: The recoil has to go somewhere, though (I believe). On the ground, that force would be absorbed by friction...which there is much less of in the air.


Furnace keeps resetting

Question: My trane xr90 furnace keeps resetting just while it
is in its "heat up phase" I'm a laymen but a description of what is happening is like this...
The furnace gets a call for heat, it makes a sound and lights up near the burners, when the burners start to heat up it makes a "whisk" sound an restarts the process. This continually happens soon after the burners begin to heat up and before the fan begins to blow the warm air into the ducts. The filter is new, the red light is blinking fast and steady (when it is calling for heat). Sometimes if I switch off the breaker and reset it will work once or twice and then start failing again. Any ideas?
Answer: Check the flame sensor.  Sounds like the furnace may not be sensing that the burners are on. Also, consult the manufacturers documentation for trouble code light sequences. The flashing light might be trying to tell you something.
Unconfirmed Trane Error Codes
Codes are displayed using a light (LED) turning on a number of times, followed by a pause. For example:
._._._.___._._._.___
. = On _ = Off
Would be read as 4 flashes, and would mean that one of the limit switches was open.

Flashing Slow - Normal - No call for heat
Flashing Fast - Normal - Call for heat
2 Flashes - External lockout, retries or recycles exceeded.
3 Flashes - Pressure switch error.
4 Flashes - Open limit device.
5 Flashes - Flame sensed when no flame should be present.
6 Flashes - 120V power supply polarity reversed, or poor grounding.
7 Flashes - Gas valve circuit error.
8 Flashes - Low flame sense signal.
9 Flashes - Check igniter.

Furnace keeps resetting


Searching dataset for Constellation detection

Question: I need to develop an Machine Learning (ML) model for predicting constellation seen in a picture taken from a mobile. This I need to develop from scratch. Firstly, I need help finding a database which can provide me images of stars with constellations labelled in it. Those can be from a ground based telescope or from a camera. This is going to be a multi-labelled problem. Even after spending hours of searching I can't find a good dataset. I want a dataset with several images (preferably a few 100), each labelled with the constellation seen in them. Then I am planning to refine them and use TensorFlow for prediction. I am a grade 12 student and still new to ML, so I really need your help.
Answer: If actual photographs are not required, Stellarium could render a suitable set of reference images.
Use the Perspective (gnomonic) projection for the closest match to a photograph, and display only the features you want.
Its scripting capability may help you avoid repeating some manual operations.
Here are a sample pair of Stellarium images.
The first has only synthetic stars, which the online plate-solving service Astrometry.net successfully recognizes:

The second is the same part of the sky with only constellation labels and boundaries:

The unlabeled region between Ophiuchus and Scutum is Serpens Cauda,
part of the only discontinuous one of the 88 standard constellations.
Comment: This could be a good method but can you tell how can I render good enough resolution pictures from Stellarium especially if pictures are needed in bulk
Comment: @HarshBanka you haven't really explained what "good enough resolution" means. **brightness:** Do you need deep sky survey images that can see way farther and dimmer than humans and cellphones, or only images that reflect what people and hand-held cameras are likely to pick up? **resolution:** Do you need super high resolution images through telescopes, or only images of similar angular resolution to what people and hand-held cameras can achieve? Is it possible to clarify those things back in your original question, rather than in comments only? Thanks!


Was the internment of Japanese Americans in WWII a public affair?

Question: Was the internment of Japanese Americans in WWII public affair; meaning, was it in any way discussed or reported in the contemporary American media? Did the authorities conduct any explanatory propaganda for the public and the Japanese being interned and relocated? My question is not about the visibility of the relocation. Of course, people could see it and people knew about it. I'm rather interested in finding out if there was any PR and public discussion involved (e.g. aimed at differentiating this from European practices of internment and exile)? If you can point me to some relevant literature on this issue, I'd really appreciate it.
Comment: What has your preliminary research shown?
Comment: Of course it was discussed.  Sons of the internees were signing up to fight for the United States. One family I know, their son was fighting Germans in Europe, with the 442nd Infantry Regiment, https://en.wikipedia.org/wiki/442nd_Infantry_Regiment_(United_States), while both parents were imprisoned at Manzanar.  They were Christian refugees from the 1920s.
Comment: @Mark I have not done any research on it. This is why I'm asking for help and literature recommendations. The secondary literature I've consulted deals mostly with personal experiences, logistics or morality of the relocation and not its public presentation in comparative context.
Answer: Since this was front page news in local newspapers (cf. San Francisco Examiner, February 1942), this was known and observed by the public:

American public opinion initially stood by the large population of Japanese Americans living on the West Coast, with the Los Angeles Times characterizing them as "good Americans, born and educated as such." Many Americans believed that their loyalty to the United States was unquestionable.
But, six weeks after the attack, public opinion along the Pacific began to turn against Japanese Americans living on the West Coast, as the press and other Americans became nervous about the potential for fifth column activity. Though the administration (including the President Franklin D. Roosevelt and FBI Director J. Edgar Hoover) dismissed all rumors of Japanese-American espionage on behalf of the Japanese War effort, pressure mounted upon the Administration as the tide of public opinion turned against Japanese Americans. Civilian and military officials had serious concerns about the loyalty of the ethnic Japanese after the Niihau Incident which immediately followed the attack on Pearl Harbor, when a civilian Japanese national and two Hawaiian-born ethnic Japanese on the island of Ni'ihau violently freed a downed and captured Japanese naval airman, attacking their fellow Ni'ihau islanders in the process.

See the references in the cited wikipedia page.
Comment: Thanks! I see that Wikipedia seems to be arguing that the government grudgingly yielded to public pressure. But it leaves it ambiguous on whether the impulse came from the wide "tide of public opinion" or from the more specific "civilian and military officials"
Comment: It appears that public opinion was the driving force behind the events.


The geth account new and web3.eth.accounts.create

Question: The  geth account new and web3.eth.accounts.create. That both function/command are same are different.To create new account.
Answer: The former is using the CLI while the latter is using the interactive interpreter shell, which calls the web3js wrapper which calls the RPC end point to create an account. They both do the same thing, but I would say the CLI has a greater degree of abstraction. It would be interesting to know if the CLI calls the web3js library or the endpoint directly


How to arrange reading for a literature review and writing it?

Question: I am a studying for a master of management. It is the first time that I will write a thesis.
I found the literature review difficult: I found several articles, but I do not know how I will do next.
Should I read the articles and highlight what seems interesting to me and then re-read them and start writing, or should I read each article and start writing in parallel?
Answer: As a professor in a French grande école de commerce, I am pretty familiar with the requirements of a literature review for a master's thesis.
I can recommend to you an article I wrote on the subject. In summary, there are eight general steps:

Identify the purpose of your literature review. In your case, it is to understand what scholars have said related to the topic of your thesis.
Plan the review. Outline the steps that you plan to take to carry out the literature review.
Apply the practical screen. That is, clearly decide what kinds of topics you will search for and which you will not search for because they are beyond the scope of your focus.
Search for the literature. Try to have a meeting with you your school library to help you understand how to use the scholarly databases and get you started in searching for the articles.
Extract the data. Read the articles and use a table to record the most important elements from each article.
Appraise the quality of the studies. This step is probably not necessary for a master's thesis.
Synthesize studies. Do not just summarize the articles one by one; rather, identify and discuss the most important themes that run through multiple articles.
Write the review. Compose and put everything together.

The article linked above has details on each of these steps.
Reference
Okoli, Chitu, 2015. A Guide to Conducting a Standalone Systematic Literature Review. Communications of the Association for Information Systems, 37(43), pp.879–910. Available at: http://aisel.aisnet.org/cais/vol37/iss1/43
Answer: General advice is below. In your question specifically, it sounds like you need to specify the particular area(s) of interest and specific research questions. Those will constrain what papers/sources to find and how far to look. The purpose is to connect what you've done with what was done before. This integration or synthesis depends on connecting the terms and methods of your work with the existing literature. So, the main task is to search and organise the previous work.
--
LITERATURE SEARCH
The purpose is a broad sweep to identify research that is relevant to a specific area or research question. When getting the scope of a literature, don't read closely, just take notes. Start by reading about the research question. If the area is self-esteem, read the article on Wikipedia to get oriented to the concepts and terms.
Also read about Boolean search logic, truncation, and wildcards. It's especially importantly to use "" to form phrases. Notice how different your results are in Google when you search social memory vs. "social memory".
If using a University library website, go there and choose the best database. PsycInfo is the central database for psychology. We also commonly use Google and Google Scholar. For medical papers, use PubMed. For economics, JSTOR. For education, ERIC.
Search! If you get too few results (usually <20), broaden your keywords. If you get too many (usually >200), use quotes, different terms, or more terms. The "right" number of results is a tricky issue to nail down. It depends on the research question. Communicate clearly with me about your search terms and database and what you're finding and I'll be able to direct you.
Good progress! Now search again using different keywords. For example, a project about randomness might include these different search terms, searched separately or together in various combinations, e.g.,: fate fatalism causation causal cause randomness meaning control "personal need for structure" "need for cognition".
Document your process. Include the database, search terms, and notes about the search process. Was it easy to answer the question? Of the citations you found, were there many more, or were you scraping the bottom?
When you find a good, relevant article, use Web of Science to check which articles have cited that article since it was published, and look for new material.
Document your findings. Using a Google document or spreadsheet, probably one that I've shared with you already, include the citation, abstract, and your summary of why you included this article, the central finding of the article, and any questions you have for me and our team about the citation.