High school experiments recommendations

Question: I am from India and you know teachers don't show the experiments and they only give the theory but I want to see experiments video at least so I'm satisfied that physics is correct , can you tell me some websites / channels which show high school experiments .
Comment: If you don't get good answers here, you might ask in [chat] either (a) about some actual recommendations or (b) about workshopping this question into a more inviting form. This is a little different from most of our [tag:resource-recommendations] questions, but I'm willing to let the community decide whether it works for us or not.
Comment: Can you specify your area of interest? Mechanics, E&M, Circuits, Optics?
Comment: Swag , ( I love EM and nuclear physics )
Answer: Well I think as you are asking for High school course, I believe that you should prefer YT videos by Walter Lewin here.
He was a professor at MIT and has an unique way of teaching the subject with the demonstrations wherever it is required. The videos cover Newtonian Mechanics, Electromagnetism, Vibrations and Waves,Bohr's model and a brief Introduction to Quantum Mechanics. Along with this he has quiz questions as well and he demonstrates them in his own way.
Answer: I advise you to do some basic experiments on your own. Like when I was a High school student, I really did some easy experiments that teach me a lot! It's true you can not do those experiment which needs expensive apparatus but still, you can do a basic experiment and learn a lot.

My favorite is A Simple Pendulum! We all know the physics behind the time period,
$$T=2\pi \sqrt\frac{l}{g}$$
Now it's time to test it! Try making your own pendulum, Measure the length of the string and take your stopwatch and record the time for several periods and see if You can figure out $g$.

I bought a multimeter so that I can do experiment with electromagnetics origin. Most of them were based on Faraday's law. Like producing the current in the coil by moving the magnet. And many others and it's fun!
I remember I take a small motor which is got from some electronic instrument, take a mobile charger lead make connected it. I take a fan sort of thing which I have fitted to the moving part of the motor, then put the fan facing the a cooler. I take the reading from the multimeter for How much the voltage motor is creating and found it was around  5 to 6 Volt and then I connected my mobile, and It starts charging. Note that It was a button mobile, not an android they take much more power.
There many things you can try!

On resources
You need to be specific here. I think googling the experiment if it's famous will give you hundreds of sites and videos that you can see. But You can watch a free course like the one given by NPTEL. Look for the course on Experimental physics like this one.

High school experiments recommendations


What is this spider from Arizona?

Question:
I live in Phoenix, Arizona, USA. Can you please identify this spider for me. Is it dangerous?
Answer: It's hard to judge from a single photo but it appears to be from the Family Theridiidae (cobweb spiders). Spiders in this family have long front (first legs)and much shorter third legs as the spider in your photo seems to have. But the perspective may be off. You don't mention the size which would help.
I enjoy photographing insects and spiders in my area. One thing I found when I was trying to identify spiders is colour and pattern can vary quite a bit from different locale. Sometimes two spiders of the same species could look like two completely different species.
So please bear this in mind. All I am is an arthropod enthusiast that has benefited from some more skilled and knowledgeable people helping me out. With that in mind, I wonder if your spider might be Phylloneta pictipes (syn. Theridion pictipes).

Source: http://bugguide.net/node/view/2209
I should've said but the two spiders above are the same species; male on the right and female on the left.
You can check out more spiders of this species at http://bugguide.net/node/view/49080/bgimage and see how they vary.
Answer: The spider is a spotted orbweaver (genus Neoscona)

Probably of the species: Western Spotted Orbweaver (Neoscona oaxacensis)
This photo I attach came from a gallery of western spotted orbweaver observations filtered on only observations from Arizona:
https://inaturalist.ca/taxa/123713-Neoscona-oaxacensis/browse_photos?quality_grade=any&place_id=40

What is this spider from Arizona?


Charge Level Control

Question: Would there be any application or method of controlling the charge level and limiting it for example to start charging at 20% and stop charging at 80% ?
Comment: Lithium based batteries get better cycle usage if you don't use the full charge level.  If you normally use 50% then using 30-80% will give you more cycles then 50-100%. If you use the phone plugged in a lot (e.g. developing) then stopping the full 100% charge will help the battery life generally.  The long term life gets worse with charge level and temperature so fully charged and in use e.g. warm is a worst case state for battery life.
Comment: why would you want to do that?
Comment: I've heard that about Lithium batteries, and I've also heard that it's an "old wives tale".  See http://android.stackexchange.com/questions/29073/battery-life-and-first-time-charging-on-li-ion-batteries-myth?newsletter=1&nlcode=36875%7c8c25.
Comment: The battery meter saying "100%" doesn't necessarily mean what it seems.  Check this article: http://phandroid.com/2010/12/25/your-smartphones-battery-gauge-is-lying-to-you-and-its-not-such-a-bad-thing/                   The signal indicator on a phone is similarly misleading, only worse.  The real reading is under about phone>status.
Answer: You could use Tasker to make a beep or push a notification when battery level is ouside your safety boundaries, so you can take an action by yourself (ie. un/plug the charger).
Go to developer website, where Tasker Userguide can help you to set that task, taking as context the State of your device.
The following image shows an example of configuring Tasker to take an action depending on battery state:
Answer: Application:
No, as for an application to do this, the answer is no since charging on an Android phone is done by its hardware! The software has nothing to do with the actual charging of the phone! (This is why your phone is able to charge even when the OS is powered down)
Method:
No, since the charging is not controlled by the software of your phone, this means it will be very difficult to stop your phone from charging (since there is no software modification that I can think of that will help... I could be wrong!)
However, as pointed out by Francisco Alvarado earlier you could create Tasker profiles to notify you about custom charge levels. Or if you are very paranoid about maintaining battery health you could make Tasker prompt you before automatically shutting down (just a suggestion).
Answer: You can hardwire it: 12 ohms in serial still makes the phone be recognized by the computer, yet slowly discharge.
Answer: Well one way of doing it would be with a device such as Raspberry Pi or similar (perhaps with java installed on it). With an add on such as Laika it can control devices including relays which could turn on/off the power to a charger. Since Android to PC communication is available over USB https://stackoverflow.com/questions/3803871/android-apps-communicating-with-a-device-plugged-in-the-usb-port then I'm guessing an app could talk to the fruity device, if not it could post to your own hosted web service. The app could then tell the device when to turn on the charger and when to turn it off according the the apps settings.
OK, a bit over the top and would need experimentation, but I think it could be done.
Lets hope that Android Marshmallow (or Maltesers or M&Ms or whatever it is) will have this built in for hardware that can support it.
Comment: It looks like RPi/Android USB communication is available, as it has been reported you can use this: http://android.serverbox.ch/?p=262

Charge Level Control


Photons, wave-like character

Question: Is it safe to assume photons really are not waves, per se? It would seem to make more sense if the electric and magnetic fields surrounding the photon are responsible for "wavelike" character, but in "reality" there is no wave action taking place. Would that be reasonable to assume? That begs the question, when a single photon is sent through a slit experiment, it can be assumed it does not interact with itself to produce light and dark wavelike pattern, but rather something else is going on?
Comment: Possible duplicate of [Slit screen and wave-particle duality](https://physics.stackexchange.com/questions/22923/slit-screen-and-wave-particle-duality)
Answer: It's a rite of passage to attempt, and inevitably fail, to explain Young's double slit experiment - so here's my ill-conceived take on it all:
When a beam is shot through the double-slit, a wave-like interference pattern is measured on the screen. However, if we "measure" which slit each item travelled through then instead a particle-like pattern is projected onto the screen. Clearly this beam is neither exactly wave-like or particle-like.

Mathematically our beam can be described by a quantum mechanical wavefunction - a probability amplitude describing our system. In this regime, saying that a photon passes through a slit is misleading. The notion of a definite position does not exist for our photons. Instead we must ask "If I made a measurement, what is the probability that the photon is at some position?".
Not measuring the slits:
We have a wavefunction describing our system and we ask "What are the probabilities of the beam hitting each position of the screen?". The beam hitting the screen is our measurement. Many photons hit the screen randomly and eventually the interference pattern corresponds to our probabilities.
Measuring the slits:
Taking a measurement is a well-defined operation is quantum mechanics. We ask "What is the probability that a photon passes through slit A THEN hits the screen at position X?". This constrains our setup to one in which each photon definitely passes through one of the slits.
In the first case noted that the wavefunction doesn't correspond to any definite position. In the second we impose that it definitely passed through one of the slits. It's this requirement that changes the interference pattern.
That may or may not have been useful, but it's how I interpret the results. Now onto answer specific parts of your question:

Is it safe to assume photons really are not waves, per se?

It depends on what you mean by "safe". Light certainly exhibits behaviour unbecoming of a wave, but that doesn't mean that it is a particle either.

electric and magnetic fields surrounding the photon are responsible for "wavelike" character

The double slit experiment seems to have the same mysterious behaviour for all items that we send through it: photons, electrons, etc. Whilst photons can be thought of as oscillating electric and magnetic fields, electrons cannot. Therefore this cannot be true.

when a single photon is sent through a slit experiment, it can be assumed it does not interact with itself to produce light and dark wavelike pattern, but rather something else is going on?

From the perspective of quantum mechanics there is no interference whatsoever. Instead we have a superposition of all of the possible outcomes, this makes no mention of number of particles. One photon passing through the experiment will only hit one location but it's probability density is the same as the one that produces the interference pattern that we saw with our beam.
Hopefully that shines some light on the problem for you. It's useful to keep in mind that in matters regarding quantum mechanics, your intuition learned from the macroscopic world may not provide any sufficient analogies to describe a phenomena.
Two more mathematically complex answers that I found particularly enlightening on this site are:

What is the wavefunction of the Young Double Slit experiment?
How is the double slit experiment modeled in contemporary physical theories?

The Wikipedia article Double-slit experiment is also quite good if you are looking for more basic information about the experiment itself. How one understands this phenomena is somewhat dependent on their interpretation of quantum mechanics. For an introduction of these interpretations see the Wikipedia article Interpretations of quantum mechanics.
Comment: Good stuff. Having a tough time wrapping around - "From the perspective of quantum mechanics there is no interference whatsoever. Instead we have a superposition of all of the possible outcomes, this makes no mention of number of particles." - it seems there needs to be a more sensible answer.
Comment: Vielbein and @therr, why the interaction of the edges with the photons is not taken in account? The light has a magnetic and an electric field component and the surface electrons of an edge have too. https://physics.stackexchange.com/q/158105

Photons, wave-like character


Is there a general theory of models that has as instances classical FOL, classical propositional logic, etc.?

Question: Is there any general theory of models that has as instances classical FOL, classical propositional logic, etc.?
Comment: Not sure whether this is what you have in mind, but there is Abstract Model Theory, where one certainly considers classes that are not axiomatizable in first order logic (or in several versions of infinitary logic). The standard reference is "Model-theoretic logics", http://projecteuclid.org/DPubS?service=UI&version=1.0&verb=Display&handle=euclid.pl/1235417263
Comment: But you seem to have a more general notion of model (structure) in mind. You may then want to look into Algebraic Logic, en.wikipedia.org/wiki/Algebraic_logic and particularly into the topic of algebraic semantics.
Answer: This depends strongly on the extent of your "etc."  For example, classical FOL and classical propositional logic are special cases of multi-sorted classical FOL; propositional logic is the case of 0 sorts.  A better answer is a pointer to the book "Model-Theoretic Logics" (Springer, 1985) edited by Jon Barwise and Sol Feferman, particularly the first two chapters, "Model-Theoretic Logic: Background and Aims" by Barwise, and "Extended Logics: The General Framework" by Heinz-Dieter Ebbinghaus.  The general idea is that an abstract logic determines, for each vocabulary (= language = signature) a collection of sentences and a satisfaction relation between structures and sentences, all subject to some very basic axioms (e.g., isomorphic structures satisfy the same sentences).
Answer: What you are after is institution-independent model theory, for which Diaconsecu has a recent textbook account. Here the bare concept of an institution is basically that of a logical system absent particular distinguishing features; things such as classical first-order logic, higher-order logic and intuitionistic logic are then instances of institutions.
Answer: In general you can pick any set of properties regarding the model theory of logics you are interested in and create an abstract theory about them. Most of these will not be interesting for various reasons but some will be. An example of nice class of model theoretic properties is those chosen for Abstract Elementary Classes. You may want to check John Baldwin's slides to get a feeling of the model theory that can be derived using such simple model theoretic axioms.


Is there a way to obtain old Salmon Run clothing?

Question: I've been playing a lot of salmon run lately. I started playing a few months ago and didn't know about Salmon run till now. I've seen many people that have the old prizes from salmon run and I would like to know if there is anyway I could obtain them?
Answer: Pink Capsules!
As you earn points doing salmon runs, you'll unlock various capsules (and the latest piece of Grizzco gear). Go to the window to the left of the entrance to the Salmon Run lobby, and you'll be able to obtain the reward from all your earned capsules.
Per the Wiki:

Blue Capsules: Drink Tickets
Green Capsules: Ability Chunks
Orange Capsules: Multiplier Tickets
Pink Capsules: Grizzco Gear
Yellow Capsules: Cash

(Note that all capsules besides the pink capsule have a 50% chance of containing 4000 gold rather than their standard reward, pink capsules will always contain a piece of gear)
The pink capsules will contain a random piece of Grizzco gear (with either 0, 1, or 3 slots filled), and includes all previous pieces of gear.


Are 401k withdrawals included in income for Medicare premiums?

Question: How do I report 401k withdrawals to Medicare if the IRS does not report it?
Comment: Traditional or Roth?
Answer: You do not need to report your income to Medicare.  Medicare looks at your tax returns to calculate the income-based portion of your premiums.
As a result, if you take taxable distributions from your 401(k), then you will report this on your tax return, and if your total income is high enough, your Medicare premiums will adjust.
Non-taxable distributions (such as a Roth IRA or Roth 401(k)) do not affect your Medicare premiums.
Source: https://www.newsday.com/long-island/ask-the-expert-lynn-brenner-1.15457896


What's the login for phpMyAdmin?

Question: I downloaded the most recent version of XAMPP (v.1.7.7) and decided start a database. When I opened phpMyAdmin, it alerts me there is a new version of phpMyAdmin available. I downloaded it from online, and I deleted the old version of phpMyAdmin and replaced it with the current version (v.3.5.1). I opened it up and it came up with a log-in screen. I entered in "root" without a password, but it alerts me I need one. I don't know any password nor I know any alternative log-ins. How would I log-in to enter phpMyAdmin?
Comment: what about `root` as password or `password`
Comment: root, password, and admin dont work as the password
Comment: Can you find the file `/htdocs/xampp/phpmyadmin/config.inc.php` ? Look for `$cfg['Servers'][$i]['password']` in this file if you can.
Answer: Enabling login without a password, to make it work exactly as before
You'll need to change your configuration file. Open up your XAMPP installation directory, browse to the folder phpmyadmin, and look for a file called config.inc.php. If there isn't one already, you'll first need to copy config.sample.inc.php to config.inc.php. Then, just open config.inc.php and find this line:
$cfg['Servers'][$i]['AllowNoPassword'] = false;

Change it to:
$cfg['Servers'][$i]['AllowNoPassword'] = true;
Alternatively, just add a password
Open a command prompt and type this, followed by Enter:
mysqladmin -u root -p pass

When it asks you for the current password, just press Enter again. Then set the new password, and log in to phpMyAdmin using that.
Comment: Thanks! I tried this method, but I havent thought of changing the file name. ;)
Comment: @zeldarulez: Just in case you want to add a password, too... see edit :)
Comment: mysqladmin -u root -p pass      Need explanation... after what circumstances does this work?
Answer: Default is:
Username: root

Password: (just leave it blank)

The Password is set to 'password' in some versions.
Answer: In new versions note that you have to change your code to like this:
mysqli_connect($mysql_hostname, $mysql_username, $mysql_password, $mysql_dbname);

And for more look to this:
Fatal error: Uncaught Error: Call to undefined function mysql_connect()

What's the login for phpMyAdmin?


Differentiate function with respect to multiple variables?

Question: So for functions with two or more variables, we can calculate partial derivatives and from what I know, this can only be done for one variable at a time. So for instead, if we have a function $f(x,y) = 2x+y^3$, we can calculate the partial derivatives $f_x(x,y)$ and $f_y(x,y)$. But is it possible to calculate the derivate of functions of multiple variables, like $f$, with respect to multiple variables - so for example to differentiate $f$ with respect to both $x$ and $y$ at once?
Answer: There are two different notions that might be like what you are looking for, but neither is really simultaneously differentiating with respect to multiple variables.
The first is that we may take the partial derivative of $f$ with respect to one variable, say $x$, and then differentiate that partial derivative with respect to another variable, say $y$. This is denoted $f_{xy}$ or $\frac{\partial f^2}{\partial y\partial x}$. Similarly we can have $f_{yx}$, $f_{xx}$, $f_{yy}$, $f_{xyx}$, $\dots$. These are known as higher order partial derivatives. The second-order partial derivatives (e.g., $f_{xy}$) measure how the slope of $f$ in a given direction changes with respect to the direction we move our base point.
Another notion is that of the total derivative of a function. This can be thought of as the best linear approximation to $f$ at any given point. If $f:\mathbb{R}^n \to \mathbb{R}$ is a function of $n$ real variables, then the total derivative of $f$ at $\mathbf{a}$ is given by $\nabla f \cdot (\mathbf{x}-\mathbf{a})$, where $\nabla f = \langle f_{x_1},\dots,f_{x_n}\rangle$ is the gradient of $f$, i.e., the vector of partial derivatives with respect to each input. This gradient records the slope of $f$ in all coordinate directions.
Comment: I'd like to add some generality to this answer: A function $g:\Bbb R^n\to\Bbb R^m$ can be decomposed into $m$ "component functions" $g^1, g^2,\ldots, g^m:\Bbb R^n\to \Bbb R$. The total derivative at a point $x$ becomes a matrix containing the different partial derivatives of the different component functions called the _Jacobian_ of $g$ at $x$. It corresponds to the linear map that best approximates $u\mapsto g(x+u) - g(x)$ for small $u$. The gradient is a special case, and the regular derivative of parametrised curves $\Bbb R\to \Bbb R^m$ is a special case too.
Comment: Thanks for the input!! But "neither is really simultaneously differentiating with respect to multiple variables" - so what would you do if you had a function f(x,y) and you wanted to find the slope of f(x,y) as x and y change? Or a function g(x,y,z) and wanted to find the slope, or the change of g, as x and z change?
Comment: @ThatGuy I would use the total derivative. This gives the best local approximation to how $f(x,y)$ changes as $x$ and $y$ both change by small amounts.
Comment: Nice! And the final thing: "Or a function g(x,y,z) and wanted to find the slope, or the change of g, as x and z change?" - what about that one? You have then answered all my questions and there are no reasons not to accept your answer :))
Comment: @ThatGuy As only $x$ and $z$ change, not $y$? Presumably then you are looking at a fixed value $y=y_0$, and you can view $g(x,y,z)$ as a function of two variables $\tilde{g}(x,z)=g(x,y_0,z)$, and apply the same techniques as for a function of two variables.
Answer: I think what you need is the idea of directional derivative. It includes the special cases of the partials with respect to single independent variables at one extreme, to the idea of gradient or total differential at the other extreme.
In particular, though, the type of directional derivatives you need specifically are those which always have at least one of their coordinates equal to zero -- in other words, derivatives in a direction parallel or perpendicular to a coordinate axes, plane, etc.
In general, when we take directional derivatives, these are given by a linear combination of the partials with respect to each independent variable, where the coefficients form a vector of unit length. That is, given a vector $(a,b,c,\dots)$ with $\sqrt{a^2+b^2+c^2+\cdots}=1,$ we call the combination $$af_x+bf_y+cf_z+\cdots,$$ with $f$ being a function of the independent variables $(x,y,z,\dots)$ a derivative in the direction $(a,b,c,\dots).$ The types you are talking about here are those for which at least one of the coordinates $a,b,c,\dots$ vanishes.


Calculus Word Problem Related Rates

Question: A spotlight on the ground shines on a wall $12 m$ away. If a man $2m$ tall walks from the spotlight toward the wall at a speed of $1.6 m/sec$, how fast is the length of his shadow decreasing when he is $4m$ from the building.
Comment: the height of the shadow is determined by drawing a line connecting the spotlight to the man's head, and then extending it to the wall. Notice that the shadow height will decrease down to $2m$ (it cannot be shorter than the man).

Also, your second paragraph is not right. You are suggesting to subtract the height of the man from the volume of a cone. Assume everything is 2-dimensional. You are interested in the length of the shadow, not in any areas involved.
Comment: what should the formula be then?
Answer: Hint:  if you draw a picture, there are similar triangles that let you find a relation between the distance between the man and the wall and the height of the shadow.
Added:  Let us measure from the spotlight at $x=0$ with the wall at $x=12$.  The height of the shadow is then $\frac {12}x \cdot 2$ meters from similar triangles.
Comment: Can you please try to explain to me what the first step would be? I am really lost on this question.
Answer: First, throw variables at it:
$x$ = distance from man to wall,
$y$ = height of shadow on wall;
$12-x$ = distance from light to man.
The triangle formed by the light, the man's feet and the man's head is similar to the triangle formed by the light, the bottom of the wall, and where the light hits the wall.  Using properties of similar triangles, we can say
$${12-x \over 2} = {12 \over y}$$
$$12y-xy=24$$
Now, take the derivative of both sides:
$$12dy-xdy - ydx=0$$
$$dy={ydx \over (12-x)}$$
$dx$, the change in $x$, is given as -1.6m/s(negative because the distance to the wall is decreasing) and $x$ is given as 4. Using similar triangles, we can calculate $y$ at that point to be 3. Substituting, we get $$dy = -.6m/s$$ The shadow is moving down the wall at 0.6 meters/sec.

Calculus Word Problem Related Rates


Recovering Oracle Database using RMAN

Question: I am an accidental DBA..I have to restore an oracle database using RMAN utility. I don't know anything about backups and restoration and this is my first assigned task. Are there any good forum(s) that has specific information and scripts that I could use for doing the recovery? I need your advice on this. Once the database is restored, what queries should i run to test if everything is ok?
Comment: Unix or Windows? Do you have any experience with Oracle? Is it a disaster recovery scenario with a backup and a new server or is everything already there on the server? Talk us through the situation....
Comment: As others have said, the best way is to practise.  The Oracle docs are very detailed and can be intimidating.  However they do have all of the information you need, even if you don't know what it is yet.  The best way to ask questions here is to ask specific questions about specific things because answering something like this is really tough.
Answer: My advice:
If this is not a production database, read the manual, try the things you learn by reading the manual and bring specific questions to specific efforts that you've hit a bump in the road.
If this is a production database, hire a professional Oracle DBA. Immediately.
Comment: I will be updating my test server and not the test. I will definitely go through some of the sources mentioned here and try out things and if I hit a bump, I'll get back to the forum and let you know about it and ask your advice. The way it is set up is the production server is backed up daily. I think I will have to copy the backed up files on to my test server and use the RMAN utility to restore it.. I will let you know... Thanks a lot!
Comment: Good luck and do come back with specific questions. You will be well received with them. General help to such a massive area of knowledge is not conducive to Stack Exchange.
Answer: The speech is quite long and complicated. However, the online documentation is really great.
So take this answer as a very brief and standard guideline on RMAN. The question is fairly generic, then the answer will be generic.
Introduction
The Recovery Manager (RMAN) utility is a way (available since Oracle 8i at no extra charge and recommended by Oracle) to provide backup and recovery activities, including full and incremental backup, reporting, detection of corrupt blocks, copy, restore and recovery of datafiles, control files, archived redo logs and spfiles. You can use either a GUI or command-line mode.
Alsp you should build the repository. The repository is a very helpful separate source that contains the metadata about your taget database and all of the backup and recovery information for that database for maintenance purposes. This information can be used, for example, to restore files and recover the database by issuing very simple restore and recovery commands.
This repository can be implemented in one of two ways: control files and recovery catalog database (recommended by Oracle).
Some operations in SQL*Plus
1) Let's create RMAN tablespace, catalog and user, and grant the authority to perform RMAN operations:
create tablespace rmantab datafile '/path/rmantab.dbf' size 50M;
create user rmanuser identified by <password> temporary tablespace temp default tablespace rmantab quota unlimited on rmantab;
grant connect, resource, recovery_catalog_owner to rmanuser;

2) Let's create recovery catalog and register target database with the RMAN catalog:
> rman catalog=rmanuser/<password>@<ORACLE_SID>
RMAN> catalog rmanuser/<password>@<ORACLE_SID>
RMAN> create catalog;
RMAN> exit;
RMAN> connect catalog rmanuser/<password>@<ORACLE_SID>
RMAN> connect target sys/<sys_password>@<ORACLE_SID_OF_TARGET_DB>
RMAN> register database;

3) Let's perform a back up of entire database:
RMAN> configure default device type to disk; --set the default backup device to disk
RMAN> configure controlfile autobackup on; --include control file and spfile with every backup
RMAN> backup database plus archivelog; --backup also database and archivelogs
RMAN> exit;

4) Let's set up the environment for a restore and recovery:
RMAN  can automate file restores and can be used to restore datafiles, controlfiles, and archive redo logs. You can perform every RMAN operations (not only restores, like in my example) using stored scripts, which are a set of RMAN commands that are stored in the recovery catalog. This option allows you to develop, test, and save commands. The following is a sample stored script that perform a full restore and recovery, and set a new archive log directory destination:
RMAN> connect catalog rmanuser/<password>@<ORACLE_SID>
RMAN> connect target sys/<sys_password>@<ORACLE_SID_OF_TARGET_DB>
RMAN> replace script fullRestoreRecovery {
allocate channel ch1 type disk;
set archivelog destination to '/path/arch';
startup mount;
restore archivelog all; --restore archivelog files
restore controlfile; --restore control files
alter database mount;
restore database; --copy physical files from backup medium
recover database; --apply all the archivelog and redo log files to bring up the database to the point of failure
alter database open resetlogs; --create new log files (a new incarnation)
release channel ch1;
}
host 'echo "start `date`"';
run { execute script fullRestoreRecovery; }
host 'echo "stop `date`"';
exit;

Take in account that each script is related to one target database only.
Verify whether database could be successfully restored
You can use the RMAN RESTORE VALIDATE command to validating backups before restoring them. For example:
run
{
restore database validate;
restore archivelog all validate;
restore controlfile validate;
restore spfile validate;
restore tablespace users validate;
...
}

The validation is identical to a real restore operation except that
  RMAN does not write output files. The lack of error messages means that RMAN had confirmed that it can use these backups successfully during a real restore and recovery.

By default, RMAN checks for physical corruption while validating. With the VALIDATE CHECK LOGICAL command, you can also instruct RMAN to check for logical corruption (corruptions, restore).
More info here.
Answer: The best way to get a good grip on RMAN is to start learning from scratch. Being an accidental DBA, this could mean a few white-nights. RMAN is a very critical component, and not knowing how it works, might cause massive data loss. Start by looking here: RMAN DOCS & Oracle Backup/Recovery Guide
Being new into this area, I suppose that you do not know much about redo logs, archives, working in archivelog mode etc. You should also read about this. Again, Oracle docs could prove a solid source of knowledge.

Recovering Oracle Database using RMAN


Can I make a song in my iTunes library into a ringtone

Question: I have a iPhone 6 Plus and was wondering if I can use a song that I purchased in iTunes as a ringtone for my iPhone?
Answer: Yes. Follow this guide or any other after getting the song from ~/Music/iTunes/iTunes Music.

Select and edit a song
The first thing we'll need to do is choose a song in iTunes to use as a ringtone. Open up iTunes on your Mac or PC and click on the My Music tab. Choose a song that's on your hard drive then right click on it, choose Get Info, then click the Options tab.
Within the main panel you'll see settings for Start and Stop. A ringtone can only be thirty seconds long, so use these settings to isolate the part of the song you want then click OK. You won't be deleting anything on the actual track itself, so don't worry.
Now highlight the song, go up to File at the top of the screen and select Create New Version>Create AAC version. iTunes will duplicate the track, but if you look closely you'll see that the new version is only thirty seconds long. That's the one we'll use for our ringtone. Remember to go back to the original track now and untick the Start and Stop options, otherwise the track will only play that short section.
Change the file type
Highlight the short version of the song, then right click and select Show in Finder. Now you'll see the two versions of the song. The duplicate should have a 1 at the end of the name to differentiate it, and of course the file size will be smaller. To use it as a ringtone we'll need to convert the file type from .m4a to .m4r, which involves clicking on the name once to highlight it, then once again to edit the name so we can change the last three letters. Finder will then ask you if you are sure you want to use the new file type? Choose 'Use .m4r' in the pop up box to confirm. Leave the Finder window open for now, as we'll use it again in a moment.
Delete the shorter track
Return to iTunes and delete the short version of the track, remembering to check the length carefully before you do so. When prompted choose Keep File, as we want to remove the track from our music library but not our computer entirely.
Import the track to iTunes as a ringtone
Go back to the Finder window and double click the shorter file. Rather disconcertingly it will disappear from the box, but start playing in the background. Don't worry, it isn't really gone. Return to iTunes, go to the row of icons in the top left corner and click on the three dots. This brings up more options, one of which is Tones. Click this and you'll see that the short version of the song is now a ringtone.
Sync the ringtone with your iPhone
Connect your iPhone to iTunes and click on the little phone icon just to the right of the three dots. This will bring up the iTunes panel for your phone, from which you want to select Tones in the left hand column. Once inside click Sync Tones>Selected tones>then the track you've created. Finally go to the bottom right hand corner and click Apply.
Set the new ringtone
All that remains to be done now is to go to Settings on your iPhone, then Sounds, and you'll find the new ringtone at the top of the list. Tap on it to select it as your general tone.
Comment: Hi, can you give a summary of what to do? If the link dies your answer is worth nothing.
Comment: @CousinCocaine Eh, adding the body of the text counts, right?
Comment: You may need to quit and restart iTunes after deleting the new track from your library. Without this step the track would not "stick" in the Tones folder, although it appeared to import it (iTunes 12.8, Mac). Even though dragging from Finder to the Tones folder showed a "+" icon, and dropping showed activity in the status window, it would not stick until restarting.


Show all tasks of all subsites in my home page under one "All Tasks list" in sharepoint 2010?

Question: How to show all tasks of all subsites in my home page under one "All Tasks list" in sharepoint 2010 ?
The admin at home page wants to see all tasks in all subsites under one list created at home page as "All tasks list"
Kindly Help !
Answer: Best is to centralize all tasks in one list and share list view in all sub sites.
Follow below steps:

Create task list in site collection.
Generate data view webpart of task list using SP Designer and save it to site gallery.
Go to sub site. Edit page and add task list data view webpart found
  in Miscellaneous category and save page.
Edit page again. Edit webpart property. Click on Edit the current
  view link from List Views section.
Filter with Created By = [Me] and save view.

In sub site, user can see own tasks. But in site collections, all tasks are displayed in list.


What is the most secure way to store the password on a physical medium (paper, etc)?

Question: Let's assume that I have to store the password on a material medium (paper, etc). What is the most secure way to do that? I mean a way of storing the password that does not needs any electronic tools for extraction of the password.
Comment: @Aaron sure you do, to increase the bus factor, as access to a heritage, for people who don't trust their own memory, etc. etc.
Comment: What do you mean by "secure"? Do you mean confidentiality? Integrity? Or what?
Comment: You do not ever NEED to store a password on paper.
Comment: Put it in a really good safe.
Answer: How about writing it on good stock paper using a pigment ink pen so it does not fade (within a few decades).
But write only two thirds of it on one sheet, another 2/3 on another sheet, and the last 2/3 on a third piece, and give them to three (trusted, obviously) friends - that way, any one of them don't have your password, but any two of them together do.
Eg. Jim gets APPLxx, Joe gets xxPLES, and Jack gets APxxES. Any two of them will be able to reconstruct APPLES, alone they would be guessing.
Answer: I would use The Vernam Cipher. My steps would be;

Choosing a long sentence that I always remember ( example: a part of my favorite song)
Encrypt my password using vernam cipher by using my sentence as key. ( there is an online generator for it: https://www.dcode.fr/vernam-cipher, but still you can encrypt your cipher on a paper without using something electronic.)
Write the ciphertext on the paper.
When I need to read my password, I can decrypt it with my key using a simple paper again.

One problem of my idea is that the length of your cipher key must be equal to the length of your password. In addition, calculation can take some time on the paper. Note that you need to destroy your paper that you have made your encryption/decryption so that nobody can find it in your trash or somewhere.
If you can do, you can store your key in a secure place. Then you will not need to remember the key. In this case, you can make your key random.
However, Vernam Cipher is described as unbreakable crpytosystem. So I would use it if I need to keep my password very secure in an environment where I can not store my paper secretly. Referance:  Cryptology and Data Secrecy : The Vernam Cipher.
Answer: Why write it down at all? Choose a book you can find in many bookstores, select a chapter and use the first twenty words or so. You will not need to carry/keep/safeguard the physical medium. Only remember the title and chapter, and buy the book when you are safe again
Comment: The connotation doesn't matter if your solution is not writing it down at all, just remebering another password. Then you're back where you left off for _any_ reason you want it written down.
Comment: This does not work for a lot of applications, like people who doubt their own memory or want to make sure trusted people have access after their death. Also, this counterquestion is better suited as a comment, not an answer.
Comment: There are multiple solutions for confidentiality, availability, reliability, etc. The connotation of 'the most secure way' depends on context, there is not enough of that in the question to assess the best option. My solution works if your house is raided/burnt, or if your luggage is stolen.
Comment: It is just the hash function to remember: the book and chapter.
Answer: Probably using a keyed hash. You write down all your passwords on paper EXCEPT for a secret password you just have to remember. Then whenever you need to enter your password you feed it through a keyed hash function to get the actual password. You just have to pick a hash function you can do in your head. Or just pick some other "derivation scheme". The keyed hash function approach works great if you at least have a smartphone available or a computer where you can compute the hash. But if you have absolutely no electronics available... a "derivation scheme" is probably much simpler.
But this is pretty much the only feasible way I can think of. I.e. you write
ABCD as a password but your secret scheme is +1,+2,-1,+1,+2,+2,+2,+2 which turns ABCD into BDBECDEF. Not that I recommend doing this, but if I had to, I'd do it like that.
Comment: If writing down the password was to give it to someone else (bus factor), how would this work?
Comment: It obviously wouldn't. But that wasn't part of the question... so it's not part of the answer.
Answer: I guess the most secure paper password is the launch codes for nuclear missile on submarines:

On a nuclear submarine hidden in the ocean
Locked in a safe that only the captain and first officer have access to.
Only opened when required to launch nuclear weapons.

In other words, you need to define your budget and threat before you can decide the most appropriate way to secure offline passwords.


spotlight does not find text in .docx files

Question: On my MacBook Pro running Sierra I have this problem:  when I look for a text string in a MS Word ".docx" file the search function does not find it although it can be found all right when I save the same file as ".doc".
What can I do to also find strings in .docx files?
Comment: Welcome to Ask Different. Do you have any version of Word installed? Also, please edit the body with your OS version. thank you
Answer: There is a free Appstore app named Easyfind which enables you to set certain search parameters. When you open Easyfind you get the pane shown below.

Click on the Settings button in the top left corner and it opens the small additional pane on the left. You can set Easyfind to search files or folders or both and then using the small pane on the left you can click on one of the groups and be sure to add docx. After that just include your search phrase and hit the
return key.
Comment: Sorry this does not help. Also with Easyfind, I see only the "doc" file but not the "docx" file with the test string!
Comment: did you add docx to the list of file types to search?
Comment: you might try .docx
Comment: Be sure to check the "file contents" under the "Search for" header.
Comment: Sorry, I have seen your comments only now. Yes, I did all as you suggest. For "doc" it works, for "docx" it doesn't. I am getting the impression there is some incompatibility inside the docx format (inserted control characters?) that prevent the search function from finding the string (no matter if it's via Easyfind or just from the "Search" field in the "Finder" window. Any suggestion will be welcome. For the time being the only way seems to be to use doc and not docx.


Can the Ruby language be used to build operating systems?

Question: Can the Ruby language be used to create an entire new mobile operating system or desktop operating system i.e. can it be used in system programming?
Comment: The short answer: Strictly speaking, yes, but it's hardly practical.
Answer: Well there are a few operating systems out there right now which use higher-level languages than C. Basically the ruby interpreter itself would need to be written in something low-level, and there would need to be some boot-loading code that loaded a fully-functional ruby interpreter into memory as a standalone kernel. Once the ruby interpreter is bootstrapped and running in kernel-mode (or one of the inner rings), there would be nothing stopping you from builing a whole OS on top of it.
Unfortunately, it would likely be very slow. Garbage collection for every OS function would probably be rather noticeable. The ruby interpreter would be responsible for basic things like task scheduling and the network stack, which using a garbage-collecting framework would slow things down considerably. To work around this, odds are good that the "performance critical" pieces would still be written in C.
So yes, technically speaking this is possible. But no one in their right mind would try it (queue crazy person in 3... 2...)
Comment: @Kshitiz: ruby is high level. It does a lot for the user behind the scenes without telling them. This is fine for ordinary programs, but when you're talking about the kernel -- the core of the OS -- programmers NEED to know everything that's going on. Kernel and driver developers need direct access to memory, and ruby hides that from the developers. Yes, ruby COULD be retrofitted to help with these special cases, but at that point you're just re-inventing C. It's all about using the right tool for the job.
Comment: hehe ok.. chris .. but yeah i really like the code and philosophy behind ruby and really wanna know.. why people so forward in this language didnt make it an independent lang if it can be .. why depend on c or c++ if we can build up a whole new system in such a beautiful language like ruby
Comment: Ruby certainly has a nice philosophy, and it's very clean-looking. But I guarantee you tried to code a driver in ruby it would end up looking just as ugly as C (probably more).
Answer: For all practical purposes: No.
While the language itself is not suited for such a task, it is imaginable (in some other universe ;-) that there a Ruby run-time developed with such a goal in mind.
The only "high level" -- yes, the quotes are there for a reason, I don't consider C very "high level" these days -- language I know of designed for Systems Programming is BitC. (Which is quite unlike Ruby.)
Happy coding.

Edit: Here is a list of "Lisp-based OSes". While not Ruby, the dynamically-typed/garbage-collected nature of (many) Lisp implementations makes for a favorable comparison: if those crazy Lispers can do/attempt it, then so can some Ruby fanatic ... or at least they can wish for it ;-) There is even a link to an OCaml OS on the list...
Answer: No, not directly
In the same way that Rails is built on top of Ruby, Ruby is built on top of the services that lower layers .. the real OS .. provide.
I suppose one could subset Ruby until it functionally resembled C and then build an OS out of that, but it wouldn't be worth it. Sure, it would have a nice if .. end but C syntax is perfectly usable and we already have C language systems. Also, operating systems don't handle character data very much, so all of the Ruby features to manipulate it wouldn't be as valuable in a kernel.
If we were starting from scratch today we might actually try (as various experimental projects have) to use garbage collected memory allocation in a kernel but we already have OS kernels.
People are making investments at the higher layers rather than redoing work already done. After all, with all the upper level software to run these days, a new kernel would need to present a compatible interface and the question would then be asked "why not just run the nice kernels we already have?".
Now, the application API for a mobile OS could indeed be done for Ruby. So, just as Android apps are written in Java, RubyPhone apps could be written in Ruby. But Ruby might not be the best possible starting point for a rich application platform. Its development so far has been oriented to server-side problems. There exist various graphical interface gems but I don't think they are widely used.
Answer: basically yes, but with a big disclamer .. which is basically Chris' answer but a different spin on it. Since for kernel performance it would kinda suck to use ruby, you'd probably want to build around a linux-ish kernel and just not load any of the rest of the operating system. This is basically what Android does: the kernel is a fork from Linux (and is maintained close to linux), the console is a webkit screen, and the interpreter is Java with some Android specific libraries. IE, Android is Java masquerading as an OS, .. you could do about the same thing with Ruby instead of Java and only a smallish hit to performance from java
Answer: While building a whole OS from scratch in Ruby seems like
a multi-billion project (think of all the drivers), a
linux kernel module that runs simple ruby scripts does
make sense for me - even it was only for prototyping
new linux drivers.


Windows server closes TCP connection immediately after sending SYN+ACK

Question: After a proper SYN, SYN+ACK and ACK TCP-Handshake, the server immediately sends a FIN+ACK indicating a graceful connection closure. The client's HTTP requests results in RST packets from server. This happens once in a 100 concurrent calls.
I have already investigated into SynAttackProtect parameter and Backlog Queue and these were related to connection resets, so unrelated to my problem.
So in what cases will a Windows server suddenly issue a FIN, immediately after a successful TCP handshake?
Comment: what exactly "immediately" stands for?
Comment: @JanDvorak : After accepting the initial TCP Handshake with its SYN+ACK, the server sends a FIN+ACK packet to the client, thus gracefully closing the connection. The only HTTP request from the client was returned with an RST.
Answer: Http.sys intermittently ends TCP/IP connections in Windows 7 or in Windows Server 2008 R2
http://support.microsoft.com/kb/2618425
Http.sys has been superseded since that hotfix was released.  If you want a more current version:
http://support.microsoft.com/kb/2634328
Comment: Thanks for the info. But in the above two cases you have mentioned, the connection is first closed by client. In my case, the server closes the connection with a FIN/ACK even before getting the first request from the client.


What is a word for when you pass the responsibility of something to someone or something else?

Question: e.g. I x my responsibility of self-defence to the state.
Comment: I voted up two answers below - I would note that your question could be improved to suggest which answer would be better for your purpose.  If you "pass" responsibility it can mean a few things.  If you mean "assign" to another entity you might chose "delegate" where if you mean "give up" you might chose cede.  (and for that matter, 'assign' and 'give up' are other alternatives yet less exclusively tied to responsibility)
Comment: @Bread .. I agree that 'pass' in the title would fit more with "delegate" however the example of self-defense has it's own quirks to it when coupled with 'pass'.  All in all the word "responsibility" does point more to delegate too - vs "right" or "ownership" or "interests" which fit more naturally with 'cede' .. but all could use more from the OP in terms of intent
Comment: @Tom22 ~ Thank you. However, I do believe delegate may be appropriate for "pass". Are you thinking of "pass off", perhaps?
Comment: It should be noted that "passing the buck" is an idiom suggesting the "delegation" of responsibility for an action that did not have a positive effect.  Doesn't fit the stated example very well, though.
Comment: Actually you put my answer in your question: _defer_. I will no longer answer questions on this site due to what I perceive to be harassment by mods.
Answer:
Delegate: verb (with object) entrust (a task or responsibility) to another person, typically one who is less senior than oneself.

She must delegate duties so as to free herself for more important tasks.

The power delegated to him must never be misused.

I delegate my responsibility of self-defence to the state.
Answer: cede  (sēd)  TFD

To surrender possession of, especially by treaty. See Synonyms at relinquish.
  To yield; grant:

As in:

I cede my responsibility of self-defence to the state.
Answer: I entrust my responsibility of self-defence to the state.

entrust - verb - "If you entrust something important to someone or entrust them with it, you make them responsible for looking after it or dealing with it."

Example sentences from the web:

I'll entrust the job to you.
To your care I entrust the book, the embroidery frame, and the letter upon which I had begun.
People entrust their money to others, who accept the responsibility to deal with it according to the terms agreed.
He will entrust more responsibilities in your hands and elevate you to your proper status.
Answer: Devolve

transfer (power) to a lower level, especially from central government to local or regional administration.

OR

give an assignment to (a person) to a post, or assign a task to (a person)

Example sentences:

Measures to devolve power to a Scottish assembly
The representative devolved his duties to his aides while he was in the hospital
The U.S. government could devolve a certain responsibility to the states
Answer: I relinquish my responsibility of self-defense to the state.

3b : to give over possession or control of : yield - few leaders willingly relinquish power.

"Relinquish." Merriam-Webster.com. Merriam-Webster, n.d. Web. 19 Aug. 2018.
Delegate tends to imply that you have the authority to insist that the delegatee accepts the delegation. It's an offer they can't refuse.
Entrust focuses on the recipient and the thing recieved. This is slightly awkward here because it wouldn't then be self-defense, would it?
Relinquish focuses on the turning over or giving up. I think it works better in this particular case.
Forgo also has the correct sense, but you can't forgo something to some one.
Forsake suggests a totality of abandonment that probably isn't wanted here.
If you take the position that the state legislates the rules and is the one who decides where the responsibility lay, the entire sentence is a bit off. It is the state that causes you to forgo this responsibility. But this can be a matter of degree, and if you are electing to take the fullest advantage of their protection, I think you are choosing to relinquish what discretionary responsibility exists.
Answer: Delegate
E.g. She was delegated to do the job.
Comment: This answer has already been given.


Any issues with LightSwitch Beta 2 and Silverlight 5?

Question: Just about ready to move to LightSwitch Beta 2 and was wondering if anyone ran into any issues with installing Silverlight 5 Beta after that? Thanks.
Answer: There seems to be a common problem with the Toolkit because Microsoft hasn't released one specifically for Silverlight 5. That's all I've heard of though, if your toying around go ahead and try it, if you are doing something professionally I'd wait until the beta is over and they release.


Installing a Subset of MiKTeX Packages to use RStudio knitr PDF Compiler

Question: I would like to compile an R Markdown document using the knitr package in Rstudio on a Windows 7 OS using MiKTeX. RStudio recommends the complete installation of MiKTeX, this encompasses over 3,167 packages as of today. Installing all of the packages is not an option that will work for me. I would like to find a subset of packages which will support the use of knitr in RStudio for the compilation of PDFs. All documents will be in English and won't include mathematical notation. They will feature figures created using the ggplot2 package.
Comment: No idea about `knitr` or `R` myself but for general latex you can download a basic miktex installation and install packages on the fly - this can be quite slow first time you try compiling (if loading a lot of packages) but possibly that can be used as a sort-of auto detect for which packages are needed with `knitr`.
Comment: The LaTeX packages that must be installed depend of the LaTeX code generated by the markdown and the LaTeX code generated by the R chunks. May be none beside the basic MikTeX installation, may be two or three dozens of extra packages *only for that document*. If all these  packages must be downloaded and installed when you push the compile button, effectively it could be quite slow, and it can fail too.  At the end of day, a complete installation is faster and safer, at the cost of install of about 4 Gb, a ridiculous amount for today 0.25-3 Tb hard disks.
Answer: The basic MikTeX installation works fine, you don't need to install the whole lot. When you run knitr for the first time, RStudio will download and install a handful of additional packages it needs. After that you only have to add more packages if your documents contain special features.


Why does a Data Loader extraction fail when invalid custom fields are specified?

Question: I'm still trying to figure this one out but I'd like to know why a Data Loader extraction completely fails when invalid custom fields are added to the 'sfdc.extractionSOQL' parameter of the process-conf file. My trace output shows no errors nor provides a reason why the extraction process fails. I just wind up with a file containing zero bytes.
Answer: To answer your question:

Why does a Data Loader extraction fail when invalid custom fields are specified?

Because it is supposed to fail. And the failure message that you will receive whenever you specify an incorrect field will be as below:

No such field [field name] on entity [object name]

Further, for:

My trace output shows no errors nor provides a reason why the
extraction process fails.

These errors are generated at the application level (in this case its the data loader). In event of any failures, the error messages are displayed on the console from where you are running the process. However, there is no option though to capture such failures by specifying any specific file in your local folder. But, you can see any such failures in a file called sdl.log which is generated by data loader in the temp directory. Refer to this link for details. Excerpt from the link below:

The log file, sdl.log, contains a detailed chronological list of Data Loader log entries......The log file can be opened with commonly available text editor programs, such as Microsoft Notepad.
If you are using Data Loader for Windows, view the log file by entering %TEMP%\sdl.log in either the Run dialog or the Windows Explorer address bar.
If you are using Data Loader for Mac OSX, view the log file by opening terminal and entering open $TMPDIR/sdl.log.
Comment: Thanks Jayant. Do you happen to know where I can find documentation discussing its designation to fail? Whatever I have so far isn't in-depth enough.
Comment: I didn't quite follow, are you looking for the documentation on why it fails when invalid fields are mentioned in the soql?
Comment: Yes. I went through what Salesforce had online and multiple learning books, however none of them mentioned this, so I'm suspectiing what I have so far doesn't cover the in-depth info I need
Comment: Well I haven't really seen any exception repository kind of documentation by Salesforce. But this (and for most of others) is kind of a self explanatory and if you look around, based on developers like us, this exception says that you are trying to access a field which does not really exist on the object.


Is it better to present a bad paper at a conference or cancel?

Question: I'm a PhD student who recently had an abstract accepted for a conference. It was based on a survey that was scheduled to take place before the conference, but external issues caused the survey to be delayed. I don't have the data I thought I would. I've tried to rework a paper that is more theory-based and introduces some descriptive data from another data set, but it's not a strong paper. Should I cancel late notice or just suck it up? It would be my first conference.
Comment: When you say "a paper", do you mean that this is a conference that plans to publish an essentially unreviewed paper based on only its intended abstract?
Comment: No, it's just a presentation of a paper in progress. It wouldn't be published.
Comment: I personally dislike the idea of not publishing "low quality materials". As long as your abstract is humble and descriptive everyone who will read it will read it on their own risk. At worst, your work will keep few megabytes of disk space on some server.
Comment: What does your advisor suggest to do? They are the one in the best position to judge: they know your research, the audience, and the customs of the field.
Answer: You don't mention your exact field, but it is very common in the humanities for conferences papers to be, in effect, works (of larger scale) in progress.
One of the really nice things about that is that when you present it, you will have a number of people with expertise in your topic listening and often times will provide very constructive comments or ask questions that ultimately help you deepen or extend or improve the paper.
So as you mention, moving it to be more theory based isn't a bad thing.  You can focus on the design of your survey, and mention the intended use, and you will undoubtedly get some solid feedback (it's also totally fine to be upfront and explain why your paper doesn't match the submitted abstract/title).
The end result will be an even better survey that, once you've done it and analyzed it, will lead to a more easily published article (perhaps with another conference paper along the way).  You may also get people to come up to you afterwards who are doing similar work, and that could result in collaborations down the road.
Answer: As it is an oral presentation go and do your best. This assumes that there is some novelty and your scheduled approach is of interest. You must decorate (verbally) it and gives to the audience the envy to proceed in the same way.
You can also represent related previous data and results.
I assume that you have a minimum of a solid base, as it seems from the question. I also assume that you have limited time, say 15 minutes max.
Otherwise don't go.


Projective measurement using two mode squeezed state?

Question: Let me define two mode squeezed states as $ \left | \xi \right>_n=\exp\left(\xi \hat{a}^\dagger \hat{b}^\dagger-\hat{a} \hat{b} \xi^\star\right)\left | n,0 \right>$ where $\left|n,0\right>$ is the number state with $n$ photons in mode 1 and none in mode 2. Now, let me define a projective
measurement $\{\left | \xi \right>_n\left<\xi\right|,\mathbb{I}-\left | \xi \right>_n\left<\xi\right|\}$. Is it possible to implement this projective measurement in the lab? have you seen any paper which has been discussed such a measurement?
Comment: Are you happy with a destructive measurement, or do you want a non-destructive measurement?
Comment: What is |n,0>? If |n> is a Fock state, how is this a two-mode squeezed state?
Comment: $|n, 0)$ is the number state with n photons in mode 1 and none in mode 2 and I applied two mode squeezing operation on this state!
Comment: By "squeezed state", people usually mean a squeezed coherent state.  Your state isn't even gaussian.
Comment: You are write, its not gaussian. Some older papers call this state two mode squeezed state. For example look at this one: http://iopscience.iop.org/article/10.1088/0253-6102/32/3/471/meta
Comment: Destructive measurement works well enough for my purpose!
Answer: If you are happy with destructive measurements, this can be done in principle in the lab. Let $\rho$ be the input state, and write $|\xi\rangle = S|n,0\rangle$.

Undo the squeezing transformation $S$, i.e., transform $\rho'=S^\dagger\rho S$. Note that $S^\dagger$ is just another squeezing transformation which can in principle be implemented in the lab.   Correspondingly, this means that now you need to perform the measurement $\{|n,0\rangle\langle 0,n|,I-|n,0\rangle\langle 0,n|\}$.
Use photon number resolving detectors to measure both modes.  Again, this is something which can be done in principle (to a certain accuracy).  Count the outcome $(n,0)$ towards the first outcome, and all others towards the second.

Formally speaking, what you are looking for is the probability $p_\xi$ for the first outcome, which we can rewrite as
$$
p_\xi = \langle \xi|\rho|\xi\rangle
=\langle n,0|S^\dagger \rho S|n,0\rangle
 = \langle n,0| \rho'|n,0\rangle\ ,
$$
where the last term is exactly what the proposed measurement determines.
Comment: What do you mean by "does not make any difference"?  It changes the measurement!
Comment: @Heisenberg: Some experiments do essentially this for $n=1$.
Comment: @Heisenberg It does!  The trick is that it first transforms the state to a different state, and then carries out a different measurement on the new state, which is just the same as the original  measurement on the original state!  Basically it's just Schrödinger vs. Heisenberg picture -- given your username, you should understand that ;)
 --- I'll add a formula!
Comment: Thanks, How come removing the squeezing operation deos not make any difference?
Comment: Thanks. If it changes the measurement how does it answer my question? I want a measurement that projects any state $\rho$ to $\left|\xi \right>_n$ with some probablity and by performing the measurement over and over I aim to somehow calculate the fidelity between the $\rho$ and $\left|\xi \right>_n$. I do not know if the scheme you proposed is able to solve my problem.


Validation method with outliers

Question: I have a method for prediction in a regression problem with outliers. I'd like to make a validation of my approach. How to make it considering that I need to have outliers in train and test datasets?
Comment: Why do you believe that outliers need to be handled differently from other data points?
Comment: If I use a k-fold, I'll have samples without outliers in training then,  the model will be adjusted incorrectly.
Answer: You could write a code to do have a fair distribution of outliers in both training and test sets for your cross-validation. So cross-validation will not be totally random, but it will represent more the distribution of your data. Then validate your model on an independent test set that also contains outliers and have a deeper look at the prediction for these outliers (are they correctly predicted or not?) to see if you should adapt model training or your dataset.

Validation method with outliers


does damaging craft influence tactical battles?

Question: If I attack but do not shoot down a UFO, and then it lands and I send in a skyranger, will I be facing less live aliens than if it had landed fully unmolested? Does damaging the UFO have any effect, or must you fully shoot it down?
Comment: @Aubergine - you, you *don't still play X-Com on a regular basis?* ;-)
Comment: I'm 90% sure if it lands on its own, even if its taken damage, it is as if it was not shot at at all, on the battlescape.
Comment: I'm with Raven Dreamer on this one. From the few times I can recall this scenario playing out, I remember that after landing next to the alien craft it did not appear to have sustained any damage. Sadly, this was not something I did recently, so I can't be certain.
Answer: No, it doesn't.
As usual, the UFOpaedia has all the relevant information, in this case in the article about battlescape map generation.
Specifically, down at the bottom of the page is the description of how the game determines when and how to damage an alien craft:

If the mission is against a crashed UFO, all UPSs present in the
  craft have a 75% chance to explode (assuming the detonation of another
  UPS doesn't destroy them first). This is performed during a hidden
  "first turn" (actual game play always begins at turn 2).

Landed UFOs have this check not done thus don't get damaged. Without those explosions all spawned aliens are still alive when the battle starts.


Please find the radius of the circle.

Question:
Hello,
I want to find the radius of red circle. I tried it with several ways like trigonometric. But there is a special value is given with this. I can not understand why it is given. It is the blue colored value "2", the distance between two arcs of circles. Please help me to find this.
Thank you.
Comment: Apparently someone likes neither this question nor any of the answers, but they don't care enough to explain why.
Answer: Strictly speaking, you do not need the information shown in blue,
because you can deduce it from the other information shown on the diagram.
Hence there is really no reason why that particular piece of
information is given.
The important thing in this problem is that you can determine exactly
where the red circle intersects the $45$-degree diagonal line
as shown in the diagram.
You know that the green circle has radius $20$ (because two of the radii
are explicitly labeled $20$), so you know the portion of the diagonal line
between the circumference of the green circle and the center of the green circle (the green dot) is $20$.
To determine exactly where the red circle intersects that line, you can
use the information that the distance from that point to the green dot
is $18$ (as shown on the diagram), or you can use the information
that the distance from that point to the circumference of the green
circle is $2$, which means the distance to the green dot is $18$.
The reason it is important to know where the red circle intersects the
diagonal line is that three points determine a circle.
You have two points on the red circle (where it intersects the green circle),
so this third point determines the center and radius of the red circle.
That is the abstract reason why the information in the diagram should be
sufficient to answer the question.
But as to exactly how to use that information, here are some hints:
Use the two perpendicular black lines as axes of a Cartesian coordinate system
such that the green dot is at $(0,0)$
and the two intersections of the two circles are at $(0,20)$ and $(-20,0)$.
In that case, we can see that the red circle also passes through the point
$(-18\cos\frac{\pi}{4},18\sin\frac{\pi}{4}) = (-9\sqrt{2},9\sqrt{2})$;
that's where the red circle intersects the diagonal line in the upper left quadrant.
Let the coordinates of the red dot be $(x_0,y_0)$. Then $y_0 = -x_0$,
so we can write the coordinates as $(x_0,-x_0)$.
The distance from the red dot to $(0,20)$ is
$\sqrt{x_0^2 + (-x_0 - 20)^2}$
and the distance from the red dot to $(-9\sqrt{2},9\sqrt{2})$ is
$\sqrt{(x_0 + 9\sqrt{2})^2 + (-x_0 - 9\sqrt{2})^2}$.
These two distances must be equal (because each is a radius of the red circle), that is,
$$\sqrt{x_0^2 + (-x_0 - 20)^2} = \sqrt{(x_0 + 9\sqrt{2})^2 + (-x_0 - 9\sqrt{2})^2}.$$
Solve for $x_0$.
(Hint: simplify the last equation so that you can apply the quadratic formula.)
With that information, it is easy to find the radius of the circle.
Answer: Hint:
$R^{2}=20^{2}+(R-18)^{2}-2\cdot 20\cdot (R-18)cos(135)$
$R$=radius of the red circle.

Please find the radius of the circle.


To go from LEO to LLO describe a Bi-elliptic/Hohmann transfer burn sequence?

Question: Being a newbie, I humbly submit the following question :
How to minimize the energy (in terms of delta-v burns) to transfer a mass of 1 metric ton (1000kg) from Very Low Earth Orbit (say 200km above sea level) to Low Lunar Orbit (say 100km above the moon's surface) using a Hohmann transfer burn sequence (or Bi-elliptic which can supposedly be even more energy efficient)? The idea being to sacrifice the transit time to LLO in order to minimize propellant and engine power even if this requires a very large number of small burns (incrementally enlarging LEO to MEO to GEO and finally reach the equilibrium point where Earth's gravitational pull equals the moon's then slowly cycle down to LLO).
Comment: Should be noted there is an another way to save propellant during Earth-Moon transfer. You can read about 'ballistic capture'. https://en.wikipedia.org/wiki/Ballistic_capture  Several spacecraft have used it, and it is more effective than Hohmann transfer (but takes longer time, up to several months to reach lunar orbit after launch).
Comment: different questions but related and some potentially helpful [How much thrust needed to move 6,000 kg from LEO to Lunar Orbit?](https://space.stackexchange.com/q/23396/12102) and [Is there a fairly detailed outline of CAPSTONE's "highly efficient ballistic lunar transfer trajectory" from LEO to lunar near-rectilinear halo orbit?](https://space.stackexchange.com/q/54746/12102) and [Going from LEO to lunar using only low-thrust ion propulsion - can it be done?](https://space.stackexchange.com/q/28037/12102)
Comment: and [Why is NASA redirecting an asteroid to Lunar Orbit instead of LEO?](https://space.stackexchange.com/q/12459/12102)
Answer: These all look like real trajectory design concepts, so let's go through them in reverse order:

incrementally enlarging LEO to MEO to GEO and finally reach the equilibrium point where Earth's gravitational pull equals the moon's then slowly cycle down to LLO

This in inefficient, as it takes both more time and delta-v than going straight into a transfer orbit and then braking at the end. The only reason you would do this is if your engines aren't capable of rapid acceleration, which is the case for ion engines. This slow spiralling costs them delta-v, but is still a net win due to the much higher efficiency of the engines.
For a very gentle spiral, the delta-v cost between two circular orbits is simply the difference of the orbital velocities (fun thing to prove!). So, at least from a patched-conics perspective (we have "zero" velocity relative to the Moon when encountering it), we have:
$$\Delta v = v_{LEO} - v_{Moon} + v_{LLO}$$

or Bi-elliptic which can supposedly be even more energy efficient

A lunar transfer is really neither a Hohmann transfer nor a bi-elliptic transfer, as those apply to a target circular orbit, crucially with no Moon there. Nevertheless, the same idea for why bi-elliptic transfers are sometimes more efficient can be applied.
To scale: consider the difference lunar transfer orbit (blue) and the almost-escape trajectory (black). The cost difference from LEO (very small circle) is very low. We can see why from the vis-viva equation:
$$v = \sqrt{\mu \left(\frac{2}{r} - \frac{1}{a}\right)}$$
Both of these orbits have a large semi-major axis, so $\frac{1}{a}$ is almost zero.

Now suppose we do a very small burn "at infinity" (far away), again at close to zero cost, returning on the purple trajectory.
The savings come from the velocity difference between the Moon and the purple orbit is now smaller than the velocity difference between the Moon and the direct transfer orbit. Which saves some propellant when slowing down.
In reality, this gives very little benefit for the much longer time spent, and real world examples often combine this with subtle 3-body effects like multiple lunar flybys and having the Sun bend the trajectory slightly while far out from the Earth.
Comment: Absolutely spectacular response, so let's try to make it concrete...say NASA decided to test a small ion engine in real conditions by sending from the iss to LLO a tiny image sensor camera chip with the smallest transmitter possible (and appropriate solar panels or plutonium radioactivity power source) propelled and guided by a  small ion engine. How many ion burns would be needed? How long would it take to receive images of the lunar surface from LLO?


Is there any way to view iOS device logs on the Terminal?

Question: Is there any way to view iOS device logs on the Terminal?
Comment: XCode free by Apple provides a graphical interface to pull logs and other info from your device. It's not a way on the terminal but just another option :)
Answer: i believe libimobiledevice is what you're looking for. github repo can be found here
it's a cross-platform lib talking to iDevices with no jailbrake needed. just use console command

$ idevicesyslog

you can install it via homebrew or compile from sources
macOS install via homebrew

$ ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
$ brew install -v --devel --fresh automake autoconf libtool wget libimobiledevice
$ brew install -v --HEAD --fresh --build-from-source ideviceinstaller

linux

sudo apt-get update
sudo apt-get install libimobiledevice ideviceinstaller
Comment: Please explain what exactly this is, and what operations it performs to help the user. Things to include may be usage of the commands, what it accesses, and how it is relevant to the question - From Review
Answer: Yes you can see iOS system logs from the the Mac command line.
Install Apple Configurator. It has an official helper tool to show the log files and perform other handy tasks.
<code>cfgutil syslog
</code>
The help command is quite useful and you can install it from the "Install Automation Tools..." menu item once you run Apple Configurator 2
Answer: Take this with a grain of salt as I have never gone looking for IOS device logs but there are apps out there (iExplorer comes to mind, there are others) that let you explore the file system of a connected IOS device and/or the contents of iTunes backups of the device. That may allow you to do what you want.


How to level this area of my garage?

Question: I have an area of my garage that is lower and sloping towards the house. When the car is wet or covered in snow, it melts and runs down into this area in front of the stairs and makes a mess. Ripping out and replacing the slab is not possible right now. Is there a product I can apply directly over this concrete to prevent this from happening? I would need to raise it quite a bit on that side. Thank you.
Comment: You may be able to have that area mud jacked, a hole is drilled and a concrete slurry is pumped under the slab raising it. Judging by the crack it looks like that area of the floor may have settled. Another option is If the slope isn't that great you may be able to cut a groove in the concrete with a concrete saw so the water drains through the groove to a lower area.
Comment: i have the same problem in my garage and i just use a rubber mat like the type you would find in the kitchen of a restaurant.
Comment: Is your slab reinforced with rebar or is it post-tension (i.e., tensioned cables)?
Comment: Not sure, it's the original garage floor and the house was built in 1958.
Comment: I think it is surely rebar. You could drill a 1/2" dia hole through the slab in the middle of the puddle. I am unfamiliar with the techniques of drilling through concrete, but just by chance you would probably not hit rebar and if you did this would probably not significantly weaken the slab. Personally, I would just accept this puddling as a minor deviation from ideal.
Answer: I have the identical problem. It wouldn't be practical to try and alter the slope. You'd need a significant quantity of material, it would need to be expertly applied, and it will have a tendency to pop loose over time.
I plan on cutting in several trough drains in strategic locations. They'll be something like this:

I'll rent a concrete saw, make the cuts, dig down 6" or so below the slab and install pea gravel (to slightly increase drainage capacity), then set and anchor the drain kit. This will allow small amounts of water to collect and percolate into the soil inside the garage, which should mostly remain thawed.
I plan on oversizing the cutouts a bit so I can anchor the drains in new concrete. I'll then epoxy the entire floor.
In your case, I'd probably install the drain crossways right through that deeper puddle. This will serve to intercept flowing water as well as drain any that manages to get around to the back side. It'll also keep the drain away from vehicle traffic. They're designed for it, but your anchoring would have to be done very well.
Comment: Drains like that are commonly installed during construction in my area (where winter is real). There's no structural concern in most cases.
Comment: This situation is not ideal, but I would never diminish the integrity of the slab by installing a large, deep drain to alleviate the problem. If pooling makes a significant, credible slipping hazard, then I would place a metal mesh mat on the slab in front of the stairs and see how that would work.
Answer: Agreed that leveling the floor is very hard, and doesn't even address the water issue (if the floor is level, then the water will just pool around your car?  you would actually need to slop the whole floor to drain out the garage to solve the problem).
To directly address the water:
if you have to move gallons of water each day, then your only option is some kind of drain (i upvoted the other answer).
However, if we're only talking about 8oz of water each day, then we want to solve this problem CHEAPLY:
I would put some rugs or rubber mats down around this area.  You can get cheap ugly rugs secondhand, consider them disposable (in terms of car oil or whatever), if they last a year or two then they have done their job.
Additionally, if you have a box fan laying around, buy a $15 dollar timer and position the fan next to the stairs.  Then you can schedule the fan to run an hour or two each night to speed up evaporation in the area.

How to level this area of my garage?


Assign posts to taxonomy terms instead of the taxonomy terms to posts?

Question: So I have a custom post type (people) with a related custom taxonomy (directory).  Instead of editing a person and then choosing the related directory organizations I'd like to "edit" a directory org and choose the people that belong to it.  Anyone know of a plugin that allows this?
I could build my own plugin with an interface to do this - looking for opinions here to.  Thinking of doing something like:
<code><?php
//Get all directory orgs
$orgs = get_terms("directory");
$count = count($orgs);
$orgtermids = array();
$peopleByOrg = array();
if ( $count > 0 ){
   foreach ( $orgs as $org ) {
     $orgtermids[] = $org->term_id; //Build array of term_ids
     $peopleByOrg[$org->term_id] = array(); //Build an empty array() for each term_id
   }
}
//Get all people currently associated with a directory org
$myquery['tax_query'] = array(
    array(
        'taxonomy' => 'directory',
        'terms' => $orgtermids,
        'field' => 'term_id',
    )
);
query_posts($myquery);

if (have_posts()) : while (have_posts()) : the_post();
  $postOrgs = get_the_terms($post->ID, 'directory'); //Get directory orgs for this person
  if ( $postOrgs && ! is_wp_error( $postOrgs ) ) {
    foreach ( $postOrgs as $postOrg ) {
      $peopleByOrg[$postOrg->term_id][$post->ID] = $post; //Store person info with each org it belongs to
    }
  }
endwhile;
endif;

//Step through and create interface to choose additional people for each directory org
//code TBD
?>
</code>
Any ideas or opinions?

Just thought of a better way to do this by extending the Walker class with a new class based on Walker_Category.  I'd have to modify this to create a form where people could be assigned to directory orgs instead of displaying as a list (directory orgs are hierarchical).
Answer: I think the "Featured Post Manager" plugin will be closer to what you're looking for:
http://wordpress.org/extend/plugins/featured-post-manager/screenshots/
The language used is somewhat confusing, and it may not work for custom taxonomies (directories) or custom types (people), BUT you can probably take the code and customize it to work for those classes of things instead, as well as updating the language used on the page.
It's mostly a single PHP file, so you'd just have to look at the code ( http://plugins.trac.wordpress.org/browser/featured-post-manager/trunk/fpmngr.php ) and change a couple things from "category" to "directory" (line 81), and "post" to "person/people" (line 108), etc.
Answer: I hope I'm understanding your question correctly here. But from what I can understand you'd like a way to select any number of custom post types on the taxonomy edit screen.
You might want to take a look at the Advanced Custom Fields plugin by Elliot Condon. The plugin features a 'Relationship' field type that might be just what you're looking for. The Relationship field allows you to select any number of posts to associate with the term. A single field or a group of custom fields can be applied to a specific taxonomy (rather than to a post editing page) if you wish.


What is the proper use of phonetic alphabet for the weak "e" in Joseph?

Question: I recall seeing an italicized 'i' to indicate that the second vowel in Joseph should be pronounced like the weak sound of the second vowel in "tendon," instead of a regular "i" sound. Can you tell me about any incidents of similar phonetic alphabet usage on the weak "i" sound elsewhere?"
Comment: Could you please distinguish between the phonetic alphabet, which is clearly not what you mean, and whatever relevant it is that specialists mean by that which I, through ignorance, term "phonetic notation"?
Comment: Yeah, what do you mean by "phonetic alphabet"?  Do you mean the IPA, or the traditional American English phonetic notation, or something else?
Answer: IPA [ə], [ɪ], [ɪ̈], [ɨ], or [ᵻ]
If you're looking for a short answer:

In American transcriptions, Joseph can be represented as [ˈdʒosəf], or perhaps  [ˈdʒozəf] for those who voice the middle consonant.
It British transcriptions, Joseph  might be represented as [ˈdʒəʊsɨf], or perhaps  [ˈdʒəʊzɨf] for those who voice the middle consonant.

Whether those two actually represent two distinct pronunciations is debatable, but phonemically they are identical for virtually all native speakers.
It's very unclear what you mean by your term "weak e". All unstressed vowels in English are reduced, meaning that they are centralized and shortened, losing the distinctive characteristics that would otherwise let you tell one from the other if they occurred in a stressed syllable.
The IPA symbol most commonly used to represent this vowel is a turned e: [ə], which is a schwa.  For example, the unstressed vowel in each of these words is a schwa, no matter their spellings: about, token, habit, lemon, focus.
On occasion other symbols are used for partially reduced vowels, but these vary.
For some of these, including in words like system or habit, sometimes the API symbols [ɪ], [ɪ̈], [ɨ], and even the non-standard [ᵻ] are variously used to represent an intermediary state of partial reduction in words like roses as compared with Rosa's.
Whether that is actually phonemic is a matter of some debate.  See Fleming and Johnson in Rosa's roses: reduced vowels in American English. You might also familiarize yourself with the IPA vowel charge with audio on Wikipedia. The UK sound comparisons site is even more interesting.
Comment: You may want to add variants with /z/, just for the sake of completeness.
Answer: Answer to Chulsoo Chin's question about the correct weak form of  'e' in 'Joseph'. Normally, it would be the same  'i' vowel as in 'bid' or 'pit', phonetic symbol the capped lower case  'i', but it could on occasions be the 'schwa' symbol, as in the first syllable of 'amount' or 'arrive'.


Do real and reactive energy exist?

Question: Are there any such things as real and reactive energies just like real and reactive power? if so, how is reactive energy dissipated?
Answer: Energy is just power integrated over time, so real and reactive energy exists or not just like real and reactive power, respectively.
As for power, real power exists and reactive power is a mathematical convenience to simplify expressing certain things.  By using the mental shortcut of imagining imaginary power, we can simplify calculations and explain real observed parameters more easily than without.
Imaginary power doesn't exist, but the effects of it projected back to real power are real.  Large scale power grid producers and consumers are often rated in both the instantaneous real and imaginary power they are producing or consuming.  However, the same real observable characteristics can be explained other ways.  Explaining them in terms of imaginary power is merely a mental and mathematical convenience.
Comment: @Gonzik, AC (phasor) analysis "pretends" that the circuit is excited with sources of the form \$e^{j\omega t}\$, which is unphysical, so that we can just keep track of the *complex* voltage and current variables that carry the amplitude and phase information.  However, it is easy to show that this pretense gives physical results if, at the end, we add back the time dependence and then take the real part of the solution.  Now, we could do this in the time domain using real valued variables but, since we need to keep track of both amplitude *and* phase, it's far easier to do this with phasors.
Comment: So is the use of imaginary power a mathematical simplification that is hiding real physical phenomena behind it that could all be explained using real-number physics (ie things we could directly measure given the correct instruments)?
Comment: Reactive power is real. The term *imaginary power* for Q, and *real power* for P, are misleading.
Answer: First of all, remember that in the context of AC (phasor) analysis, real and reactive power, unlike voltage and current, are not phasors, i.e., they do not represent the amplitude and phase of a sinusoid in the time domain.  Thus, we cannot "tack on" the time dependence and take the real and imaginary parts to calculate the associated energies in time domain.
Sometimes it is helpful to "go back to basics" to gain insight into a problem.  This is such a case.  Reactive power is a useful concept in AC analysis but what it represents physically is best seen in the time domain.
First, consider a sinusoidal voltage source \$v_s(t) = V\cos\omega t\$ driving a resistor R.  The power delivered to the resistor is:
$$p_R = \dfrac{v^2_s(t)}{R} = \dfrac{V^2\cos^2\omega t}{R} = \dfrac{V^2}{2R}(1 + \cos2\omega t)$$
The key observation here is that the power is never negative, i.e., the flow of energy is from the source to the resistor always.  Thus, the energy supplied by the source increases over time.
The energy supplied by the source over a period \$\dfrac{\pi}{\omega}\$ is:
$$W_R = \dfrac{\pi V^2}{2\omega R}$$
Now, replace the resistor with a capacitor.  The power delivered to the capacitor is:
$$p_C = v_s(t) \cdot i_C =  V\cos\omega t \cdot (-\omega C)V\sin\omega t = -\dfrac{CV^2}{2}\sin2\omega t$$
The energy supplied by the source over a period \$\dfrac{\pi}{\omega}\$ is:
$$W_C = 0 $$
The key observation here is that the power is alternately and equally positive and negative, i.e., the flow of energy is back and forth between the source and the capacitor.  Thus, the energy supplied by the source over a period is zero.
But, as we know, the power associated with a capacitor is reactive power in phasor analysis, and now we can answer your question:

Are there any such things as real and reactive energies

We have shown that reactive power is associated with an alternating energy flow between the source and load that is zero over a period.  In other words, it is associated with the energy that "sloshes" back and forth between the source and load without any dissipation.
Answer:
how is reactive energy dissipated?

Reactive energy has no definition that I'm aware of but, it could be taken to mean the energy interactions between a power source and a reactive component. If that power source is a sinusoidal AC voltage and an inductor is connected to that source, energy flows into the inductor then out from the inductor as the AC waveform alternates. The average energy is zero i.e. the same flows "in" that flows "out" but, if a small resistor were inserted in series with the inductor both forward energy (into the inductor) and reverse energy (back from the inductor) would cause some of that energy to be dissipated as heat in the resistor.
Answer: Is there something more to Reactive Power than a mathematical convenience?
Reactive Power in the News (New York Times, Sept. 26, 2003):

"Experts now think that on Aug. 14, northern Ohio had a
  severe shortage of reactive power, which ultimately
  caused the power plant and transmission line failures
  that set the blackout in motion. Demand for reactive
  power was unusually high because of a large volume of
  long-distance transmissions streaming through Ohio to
  areas, including Canada, than needed to import power
  to meet local demand. But the supply of reactive power
  was low because some plants were out of service and,
  possibly, because other plants were not producing
  enough of it."

Resources:

Reactive Power Overview (PDF)
Google search: How does reactive power support voltage

Do real and reactive energy exist?


suspend and hibernate not working after updating ubuntu 14.04 in amd processor laptop?

Question: when I suspend my laptop then it will not open from there even I have to hard shut my laptop every time to reboot it, suspend and hibernate both are not working.
What is the problem and how to fix it?
Answer: This is the problem of your drivers of graphic card so you can update it by following commands:
<code>sudo apt-get install fglrx-amdcccle-updates
sudo apt-get install fglrx-updates
</code>
but this will work for AMD Radeon, you need to find out for your graphics driver, you can easily find these packages from synaptic package manager.


Where can I find an extensive list of Wilderness Kids products?

Question: Hollow Earth Expedition's Ubiquity System was expanded into a game called Wilderness Kids targeted to younger gamers giving them an introduction to roleplaying and the Ubiquity rules. The resources available seem to be in disarray. Where can I find a complete list of adventures and supplements for Wilderness Kids?
Comment: Surprisingly, RPGGeek doesn't have anything on this game yet.
Comment: Might be time for me to create some more official Wilderness Adventure Kids material. I am hoping that perhaps 2012 will be the year of the Wilderness Adventure Kid. I may put all other adventures (Six Guns of Death & Dirk Savage) to really get the WAKids up and going.
Comment: I haven't created any new Wilderness Kids (now Wilderness Adventure Kids) material in quite some time. This year at GENCON 2015, we'll be unveiling the latest two hour WAKids adventure (Monkey Mayhem AKA MONKEY MAYHEM AT THE ZOO). Originally planned for release in 2010 it got bumped for another project that year. It's a few years late, but we expect it to be a lot of fun. If we see sold out games, and more people asking for material I will reconsider the idea of talking to the Exile Games folks about some more adventures in what I would like to call the KIDbiquity line.
Comment: Right! I first looked there, too.
Answer: I think the following is the list of Wilderness Kids adventures and their first appearance at Gencon:

Movie Mayhem ('08)
Haunted House ('09)
Jewels of Prometheus Falls ('10)
Mummy Menace in the Museum ('10)
Monkey Menace at the Zoo ('10)
Revenge of the Saucer-Men ('10)
Tentacles of Terror ('10)
Treasure Trouble ('10)
Save Christmas ('11)

So far, only Movie Mayhem is complete at the Mythic Eras Site.  My draft version of the WK Save Christmas is also there.  The original and my "alternate" version of the PC's are also at Mythic Eras site.
Answer: Well, here's the thing. Wilderness Kid Adventures is not officially a separate RPG.
What it is is an idea spawned in someone's feverish mind to create adventures geared towards the younger set using the Ubiquity system. There have been a few runs created, most if not all unveiled in GenCons past.
The runs have been very well received (I believe this year's GenCon will feature at least one new adventure). It'd be great to point to some resource where the adventures were available for public consumption, but since this is really a labor of love, publication has been a bit spotty.
What is available can be obtained from the Mythic Eras site. Perhaps if a general outcry for more material is heard, the authors will feel more confident to release more of their fine creations. ;-)
Comment: Here's my +1 outcry!