Configuring Ports on a Cisco Switch

Question: I am very new to Cisco networking (haven't done any course either). I have been trying to learn a bit of networking myself and had no trouble in doing some of the basic stuff which i needed for my personal work. But i am planning to buy a new Cisco switch(a gigabit switch) and configure it to 2 different networks (1 being an internet and other being a private network for a specific job). I want to configure the ports in such a way that the first few slots for normal internet and the rest for my other network. For example if its a Cisco 2950 48 port switch, the first 1-16 port for my local internet network and the ports from 17-32 for my other network. Can somebody give me a run down on how to achieve this? Sorry for such a long but basic question, i am just trying to save few $$ and learning something new. Any help would be appreciated. Cheers
Comment: I think regarding your practice, the others have spoken. Regarding your switch related issue, I really think you'd require a router in this case if you were planning on implementing this architecture you speak of. Why because, you could use your switch to manage your LANs, but when it comes to going out to the Internet, you're going to need a router to do NATing for you or else you'll be wasting a lot of public IPs (which I doubt you'll get in the first place). Is this a job role you're trying to achieve or just for practice?
Comment: I was trying to do this for learning purpose. Just to get some hands on knowledge on configuring the switch.
Comment: Alright then. If you're trying to get some knowledge on configuring a switch, I suggest you leave out the internet/IP (Layer 3 of the OSI model) aspect of things. I suggest you go with practicing concepts like basic switching within a LAN segment, VLANs, Trunking, STPs and Port Aggregation since these are what are mainly used with Layer 2 devices (switches). You can connect two different networks together using VLANs on a switch (I doubt it's possible with c2950) but I suggest just practicing switching within a local LAN and then practicing concepts of routing which is a whole new ball game.
Comment: There are a lot of books you can buy on these topics. Check Amazon.com, Cisco.com or just browse for books on these topics.
Comment: Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
Answer: First have some simulation windows (other OS) machine by using simulators such as Packet Tracer by Cisco or GNS3. Cisco Packet Tracer will give you a head start about Cisco Routers and Cisco Switches. Try to configure them. Look at boot sequence of these network devices.
Comment: Thanks for your response Muneeb. I already bought a second hand switch and put the switch in factory default configuration by deleting all the files in flash (except the ios image) & write erase command. I hope the device is in factory default configuration. Could you tell me the steps for configuring the ports in an actual switch? how can we do it using the CLI ?
Comment: I hope you have console port. Connect Console Cable with Network Device to Computer. Open HyperTerminal, which is included in OS, connect the network device on comm port.
Once you are in user exec mode.
Comment: Once you are in user exec mode.
Switch>
Type 'enable' to go into privilege mode'
Switch#
In this mode, see interfaces by typing "show ip interface brief" command.
This is brief way of seeing interfaces that are up or down.
To configure interfaces, type "configure terminal" to enter into Global Configuration Mode.
You can configure switch interfaces on interfaces configuration mode.
Comment: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2950/software/release/12-1_11_yj4/configuration/guide/lrescg/swint.html#wp1129646
Comment: Once again thanks for your help Muneeb. I have actually got to point of global configuration mode. i am finrding difficulty after that, anyway let me just read through the link you sent me with a clear head.
Answer: This is pretty straight forward to do, especially starting with a default configuration.
If you wish to create two networks, you will need to use VLAN's. These will allow you to segment your network into logical sections.
Once you have created those two VLAN's, you need configure the ports that will reside on those VLAN's. Your VLAN that will connect to the Internet will connect to a port that connects to your ISP router.
To create a VLAN
Switch(config)#vlan 2

To name the VLAN
Switch(config-vlan)#name "Private Network"

Note: VLAN 1 always exists by default and can't be removed. So now you have VLAN 1 and VLAN 2 created
To assign the ports to the VLAN you can do something like this and also use the range command to apply this to multiple ports. This selects ports 1-16.
Switch(config)#interface range FastEthernet 0/1-16

Then configure those ports to use a specific VLAN in access mode
Switch(config-if-range)#switchport access vlan 1

There is alot more to do but this hopefully gives you a high level run down.
Hope this helps you on your quest.
SleepyMan
Comment: Thanks heaps man, I will definitely try this and let you know how it goes. Once again appreciate your help.
Answer: Packet tracer and GNS3 for simulation is a great idea to start....9tut along with the Cisco forums can also be a good source of helpful info if you are having issues grasping a concept.
If you can afford to do it I highly recommend building a home lab setup using a pre-fab home lab which you can purchase off of Ebay or the like. Usually you get a few 2821 routers and a couple of 3560 switches to go along with them, including all of the necessary add on cards. This will give you ability to run IOS 15 and get some hands on practice. The going rate is usually about 299 but sometimes you can find one on CL.com etc for less if someone is selling theirs on the cheap.
The two biggest things, read the cert guides. Those things have some valuable info if you are just starting out. Secondly, practice...practice and more practice. In my opinion hands on practice is one of the best ways to become proficient with the material along with using the concepts in a functioning environment. CCNA was a tough go, but with effort most people of average intelligence can learn and master the material. The Cisco cert courses have been some of the most valuable sources of info around, I definitely feel like without them I would have never made the jump to admin level and ultimately engineer level positions.
Comment: Thanks for your advises Ty Smith. I will surely keep that in mind.
Answer: A best way create two VLANS  in switch initially .
**Assuming two Vlans are Vlan10 & Vlan20 **
Switch1(config)# Vlan10
Switch1(config)# name internet
Switch1(config)#Vlan 20 Switch1(config)#name LAN`
Now assign Vlan 10 for range of switch ports from 1-16
Switch(config)#int gigabit range 1/1-16
Switch(config)#switchport mode access
Switch(config)#Switchport access Vlan 10
Switch(config)#no shutdown
Similarly assign Vlan 20 for remaining ports
Switch(config)#int gigabit range 1/17-32
Switch(config)#switchport mode access
Switch(config)#switch access vlan 20
Switch (config)# no shutdown

Configuring Ports on a Cisco Switch


Can I base a calculation on multiple drop-down options?

Question: I have a drop down menu with several options. Is there a way I can put a calculation based on each option? I mean, for example, lets say for a certain item chosen on drop down menu it show "3%". Then client adds on the currency field "$100".
I would like to put a calculation that would should the client the total result = "$3"
Answer: Calculations in Cognito Forms can reference all fields and perform just about any calculation you can think of.
In this example, if you have a Choice field called Discount and a Currency field called Amount, you would enter the following calculation for the discount amount:
=(if Discount = "3%" then 0.03 else 0) * Amount


Attachments not sending when emailing a contact in CiviCRM v. 4.7.10

Question: When sending an email to a contact, the email sends OK, but without the attachment. I can see from here that this is a known bug in 4.7.10, and a simple fix has been provided, which will be implemented in 4.7.11. I made the fix in 4.7.10, but it doesn't work - emails still send without the attachments. Until 4.7.11 is released, does anyone know how to make 4.7.10 work? Thanks.
Answer: Please ignore what I wrote. The fix does work. I just fixed the wrong installation. What a dork. All sorted now.


What about so-called "historical revisionism"?

Question: How do you plan to handle the inevitable invasion of Holocaust deniers, Nazi apologists and so forth? For example, the accepted answer to a question about WW2 Why did Hitler declare war on the USA? links to the webpage of an institution widely accused of skewing the history of WW2. Yet the author of the answer treats them as a trustworthy source.
Comment: How about Creationists and intelligent design?  Those I think we should point to http://www.venganza.org at the very least.
Answer: Yes, I think that this is a big problem. Consider this answer for example, 5 people apparently found it useful. Yet it lists very strange "facts" that aren't confirmed anywhere (in fact, you can easily find sources that say the exact opposite). I noted the issues and got "are we trusting KGB now" as a reply - conspiracy theory at its best.
This example shows that relying solely on the community to sort such things out will not work. Some arguments sound convincing enough to collect some upvotes - but that doesn't make them reasonable. And leaving such answers around, with upvotes and even accepted (because the OP is into conspiracy theories himself) will undermine any respect that this site might gain.
I think that we should flag such answers. Indeed, I've done that with the following explanation:

Conspiracy theory - listing "facts" that contradict pretty much all
  the sources available, not willing to share any sources that support
  these statements.

While requiring sources for everything might go too far, we should definitely ask for sources when we see statements that aren't obvious or common knowledge (meaning: not verified by a simple Google search). If the author doesn't comply within a day or two we should flag the answer for deletion.
It would be nice if we could automate this process, e.g. have a flag "sources missing" that would add a comment "Your answer makes claims that aren't supported by any sources, please edit it to add them". And that flag would only show up in the moderation queue after two days, to check whether the author complied. But for now the manual process should do as well.
Comment: @quant_dev: You cannot have an open community on the Internet and expect that only experts will participate. But I think that enough users on this site actually know something and weeding out false statements will be possible (even if it doesn't happen by majority vote a.k.a. reputation system).
Comment: You can, if there is moderation. The Usenet group `soc.history.war.world-war-ii` is a good example.
Comment: "This example shows that relying solely on the community to sort such things out will not work." - You could, if it was a community of real-world experts (aka "historians"). What we have on SE is a community of anonymous people who claim to know something. This works for stuff like programming, because the answers are easier to verify, and people are less likely to spread falsehoods for political reasons. History is, as Pynchon put it, "hir'd, or coerc'd, only in Interests that must ever prove base". I'm increasingly sceptical about the success of this site.
Answer: H. L. Mencken said: "the trouble with fighting for human freedom is that one spends most of one's time defending scoundrels. For it is against scoundrels that oppressive laws are first aimed, and oppression must be stopped at the beginning if it is to be stopped at all."
Let them ask questions and let us respond with facts and references.  Let us show with reason why they are wrong.
Asking about why some people consider the holocaust to never have happened would be a grand question -- but would need to be carefully crafted to avoid being inflammatory and comply with the rules.
Note that some of those questions may fall foul of acceptable terms and conditions of stackexchange.  I do not think that racism is addressed as such but we should contact the legal team first and foremost.  Note that denying the Holocaust is illegal in a few countries and that would be covered by the above terms.
PS: Just to make sure that everyone knows where I stand: Holocaust deniers and Nazi or Communist or any totalitarian ideology whatsoever apologists are wrong and scum.  But since I believe in freedom of expression (silly me?), they should have the right to babble nonsense as long as I (and hopefully others) can tell the world that they are wrong.
Comment: I think it is more complicated than that. Consider [this answer for example](http://history.stackexchange.com/questions/71/why-did-hitler-attack-the-soviet-union-when-he-was-still-busy-fighting-britain/113#113). Originally my answer mentioned Suvorov as a trustworthy source as well. Turns out he wasn't, something that is impossible to tell if you just read his books but don't go verify all the numerous sources he lists. There is a very real danger that we help spread misinformation without even realizing.
Comment: Oh, and you cannot beat a Holocaust denier, a creationist or a conspiracy theorist in a discussion. They have a counter-argument to any argument you can bring up and you simply cannot refute their arguments fast enough. Hoping that the discussion will somehow settle by itself is futile.
Comment: If I had any suggestions I would answer rather than comment on your answer ;)
Comment: @WladimirPalant: Good point above... What do you suggest we do?
Comment: @WladimirPalant: Okay, now that made me laugh.  Thank you!!!
Comment: Ok, now I have a suggestion: http://meta.history.stackexchange.com/questions/71/what-about-so-called-historical-revisionism/100#100
Answer: Let's make sure we under exactly what "revisionism" is.  Revisionism is in fact the perfectly legitimate academic process of questioning and, well, revising existing interpretations of the past based on an intellectually honest assessment of new information that has come to light, new ways of looking at information that had already been available, or newly-discovered flaws in the reasoning behind existing interpretations.
What you're describing is more accurately termed "negationism," so as to not confuse it with the ongoing and perfectly legitimate process of revisionism that is continually occurring (as it should be) within the scholarly community.
Comment: Excellent. I wanted to write the same: revisionism is an important part of historiography.


I need to batch convert Word (.doc) to Word Perfect documents (.wpd)

Question: Everything I have found so far is going the other direction and few specifics.  I need to convert approximately a hundred Word documents into WordPerfect documents.  It has been more than a decade since I have needed to do anything like this and I can't remember how.  Any specific suggestions or links to solutions is appreciated.
Thanks in advance.
Answer: Found a link explaining how to enable saving as a WordPerfect document in MS Word 2003, but it seems that the format is not supported by latter versions of Office/Word due to security concerns.
But if WordPerfect supports RTF (you don't specify which version of Word or WP you are using) you could use one of these scripts written by Rob van der Woude to automate batch converting documents from Word into RTF and then opening them in WP.
Hope this helps somewhat...


Large scale video conferencing

Question: Is there any way to providing video conference supporting large number of participants in conference (around 2000). The conference will be held in future and I should guaranty the performance. What is System Requirements for server.
Does anybody test "Lync Server 2013", "apache-openmeeting" or "BigBlueButton"?
Comment: Do all the users have to be able to send video or just the presenters?  Whatever you use would have to be able to select a user to present at any given time and have the video feed only sent on request or the data rates involved would become completely impossible to sustain.  You probably want to look more into remote presentation software than video conferencing software since video conferencing tends to be more of an everyone sees everyone kind of thing.
Answer: I've messed with BBB, though no where close to those numbers.  As the presenter, you can prohibit participants from sharing their video or audio, making it a one way presentation.
I have a gut feeling though, that the server requirements would be significant for that many participants.  We ran it on an old HP G3 and it worked , but slow for a dozen participants.
From their FAQ:

What are the minimum hardware requirements for the BigBlueButton
  Server As a minimum, we recommend you run BigBlueButton on a dedicated
  quad-core machine with at least 4 GB of memory and a 2.6+ Ghz
  processor.
We recommend installing BigBlueButton on Ubuntu 10.04 32-bit/64-bit on
  the server (see Installing BigBlueButton).
While the BigBlueButton VM is a good way to try out the system, we
  recommend you run BigBlueButton on a dedicated server to reduce audio
  lag. In a virtual environment, the BigBlueButton VM gets only a
  portion of the host's CPU, and any lag in the CPU cycles can translate
  to lag in processing VoIP packets.
What are the minimum bandwidth requirements for the BigBlueButton
  Server You'll need good upstream and downstream bandwidth from the
  server. We recommend (at least) 100 MBits/second bandwidth in both
  directions.

Personally, I'd probably looking into a SaaS solution like Webex, GoToMeeting, or the like.  There are probably at least a half dozen solid options.  Without having done it before, I'd hate to have sole responsibility for a conference that big.

Large scale video conferencing


Importing XML into InDesign and automatically adjusting content

Question: My client has an InDesign catalog. Instead of manually updating it as he's done up to now, he'd like to import XML data into the InDesign file and not have to make any of the changes manually. However there is one major problem, the pages in the document tend to be very uneven in their layout. One page might be fairly airy while the next may barely contain all of the elements it needs to. As a result, my client needs to make the copy smaller on some pages. Is there a way to automate the size of the text from one page to the next when making an import so as to avoid overset text?
Comment: If any of the answers below is satisfactory, please tick the "accepted answer" tickmark next to it. Good for you, me, us.
Answer: If you are making all the text in the frame smaller, you can apply a scale change to the frame itself. Then the text is technically unmodified.
Answer: Typefi autofit comes closest to that:
http://www.typefi.com/typefi-publish/typefi-autofit


Were Pharaohs still inscribed on walls and written on papyrus after their deaths?

Question: If so,  was it done for historical record, or tradition? Any details on this appreciated. Do we have any instances of artifacts depicting past Pharaohs or events that occurred before they were created?
Comment: Sorry but this question does not make sense. I assume you mean 'Were'' not 'where' but even so the Egyptian kingdom lasted a long time. Old Kingdom, Middle Kingdom and New Kingdom as well as the intermediate periods all with very different customs and habits so a bit more detail and precision would help.
Comment: Yes I know the Egyptian kingdoms but my specific question is do we have any signs or evidence of a pharaoh being depicted in Egyptian records, art, or religious artifacts after their death?
Answer: Yes, but it is unusual, particularly for inscriptions on monuments or in tombs.
To understand why, we need to understand something of Ancient Egyptian art. The key fact to bear in mind is that most Ancient Egyptian art and carved inscriptions were never intended to be seen. They were designed to benefit a divine or deceased recipient.
[If you can get hold of a copy, Principles of Egyptian Art by Heinrich Schäfer is probably one of the best texts that I know on the subject.]
When the acts of a Pharaoh were recorded, it was to emphasise his glory, to show that he had done all the things expected of him, and that (under his rule) everything in the world was as it should be. This last point cannot be understated. The concept of "rightness", that everything in the world was as it should be, was even personified as the goddess Maat. The phrase "all according to Maat" is one that recurs often in Egyptian texts.
Often, when a Pharaoh died, his successor simply appropriated their building projects, replacing their predecessor's name with their own. It was actually far from unusual for a Pharaoh to re-appropriate statues or inscriptions of earlier rulers. This helped "raise their profile" and ensure that the gods knew they were doing a good job as Pharaoh. Perhaps just as important, it also helped ensure that their name lived on after their death.
Sometimes, as in the case of the Temple of Seti I at Abydos, the monument was completed by the Pharaoh's heir (in this case his son, Rameses II). Rameses not only left his father's name in place, but added further inscriptions praising his life. Of course, he included himself in the inscriptions (extensively - and particularly in the second courtyard), noting how he had completed the work on his father's temple as a dutiful son should - all according to Maat.
It is a little less uncommon to find references to deceased (oten long-deceased) Pharaohs in text written on papyrus. The Pharaoh Khufu appears in a number of later stories, for example those in the Westcar Papyrus. These are mostly of the genre known as "wisdom literature". The Westcar Papyrus is written in Middle Egyptian and probably dates to the Second Intermediate Period, perhaps some 800 years after Khufu's death. Another example of a text written after a Pharaoh was dead is the Instructions of Amenemhat. In this case, the text actually purports to be advice given by the deceased Pharaoh himself to his son Senusret I.
As a rule, we can usually tell when the Pharaoh (or indeed anyone else, for that matter) referred to in a text is dead, since they will be given the salutation "justified" (Maat Kheru).
Comment: @MarkC.Wallace I was just looking to add some additional online sources. I wasn't sure about including Pharaohs who were expunged from the historical record (e.g. Akhenaten, Tutankhamen, Hatshepsut etc.). I don't think that's what the OP was asking about.
Comment: Sources would improve this answer.  That said, it is a very good answer since it provides the context to understand.   I'd like to see it extended to address the difference between those Pharoah who are expunged from the historical record and their names obliterated, and those Pharoah whose existence was tolerated as historical artifacts.
Comment: Good answer. It may also be worth noting that sometimes Pharaoh's were removed after their death. Akhenaten comes to mind as almost all records of him were expunged after his death and the restitution of the old religion. I think also the method of carving was changed to make this more difficult. Instead of relief carving with the carving standing out the images and hieroglyphs were inset.
Comment: @PurplePilot Yes, although it's also worth noting that, in the case of Akhenaten, they didn't deface the god's name. The "Aten" part is still visible on the blocks found inside the [pylons at Luxor](http://dlib.etc.ucla.edu/projects/Karnak/feature/AtenTemples)


Slow to open files from Server 2008r2 with exchange 2010

Question: I have a domain with windows 7 pro x86 and x64 bit computers on it.  Users are experiencing slow load times for office documents that are shared on a network share off the same server that houses the exchange2010.  The symptoms are that a downloading bar at the bottom of the document appears when they open it and then the file takes between 30secs-5mins to open.  I beleive it is happening as a result of an exchange error occuring on the server but dont know how to confirm/disconfirm this suspicion
Answer: Assuming you're just talking about files being shared out of an NTFS folder on the server computer's hard disk drive (and not something like files being shared out of an Exchange public folder) I doubt that Exchange is related, per se.
Exchange could be bottlenecking your I/O. You should look at the I/O load on the server computer using Performance Monitor and make sure that you're not building up a high disk queue on the spindle where the shared files are located.
I'd sniff the traffic between the client and the server when opening the file to see what the character of the network bandwidth utilization is. You may find that the file transfers quickly and the client spends time, following the transfer, doing something.
I suspect, based on your tag "office-2007", that you're talking about problems opening Microsoft Office files. I've had Office-aware anti-virus software negatively effect file load times and, had I not sniffed the traffic, I wouldn't have seen that the file transfer was long-since done before the client appeared to finally "open" the document.
Benchmark transferring a large file by copying it with Windows Explorer. If the file transfers quickly that way then you're probably better off delving into the Office programs' operation with something like SysInternals Process Monitor.
Answer: Echoing Evan a bit, but loading file-level AV on the same server as you're running Exchange has been known to have some strange side-effects. Especially if the Exchange AV is made by the same company as the file-level AV. The two packages I've used, Symantec Endpoint Protection and Microsoft ForeFront, were rather clear that you should not run file-level AV on the Exchange server at all. I suspect you're finding out why that's the case.
A way to test this is to see how long it takes to copy off non-Office files from those shares. If those go fast, but office does not, then the chances of a horrible AV interaction increase.
Answer: Thanks to Evan and sysadmin. Eset Nod32 4.2 file system protection caused exactly this problem. Disabling file system protection on the server with Exchange 2010 and file services did the trick


Is resistor on LED's necessary after voltage drop?

Question: Let's say we have perfect 5V DC 0.1A power supply. Obviously for one LED we would need a resistor (I'm well aware of Ohm's law), BUT what if we connect bunch of LED's in series. And the current drain is well above the power supply, so voltage on those LED's drops to 2.5-3V. Would you still need to add resistor if LED's voltage is about 3.2V? It might be a silly question, but I thought it'd be cool to not have a resistor in such case (because LED's would be brighter that way) and better ask and be sure than be sorry, right!? Thank you in advance!
Comment: LEDs would NOT be brighter that way. You would only have one way to surely avoid destroying your LEDs with your scheme: if the minimum forwarding voltage is more than the voltage from your power supply. But that would mean your LEDs will not light up at all.
Comment: hmm. interesting. I thought that the difference between the LED max forward voltage and source voltage divided by current drain would determine the resistor we would want to use. meaning that if we got perfect 3.2V source and max 3.2V forward voltage LED the difference would be zero, so zero divided by current drain we'd have zero ohms. Was I thinking wrong the whole time?
Comment: Yes. If you use the LED *max* forward voltage for calculations, you'll overdrive your LED, because the actual forward voltage is always less than the max value. You should use the *min* forward voltage for calculations - in that case you'll always underdrive your LED.
Comment: Since you cannot know the exact voltage the LED needs (you only know the possible min & max values), you'll have to be prepared for the maximum as well (so your voltage sources *has to* provide at least the max voltage there), otherwise your LED may sometimes not light up. But, you have to be prepared for the min value as well, that's why you need the resistor.
Comment: Well you are kind of right if the LED's total forward drop could stay nice and steady at the 3.2V. Unfortunately the forward voltage changes some when current changs so if you had multiples of these ~3.2V LED strings would likely see intensity variation between them. Some might not even light.
Comment: Yes, I see. You both make a good point. First of all - intensity does changes meaning that voltage is divided not evenly (that's why we double feed led strings). And I kinda see Laszlo's point, yea I guess from now on I'll use minimum forward voltage for calculations instead of max forward voltage. But brightness does change, then again I was using LED's with max forward voltage till now. Perhaps I shortened their life significantly.
Answer: Short:
GIVEN:

A Power Supply (psu)
Providing Vcv (V constant voltage)
with maximum current = Icc,
and providing Icc at reduced voltage when R load < Vcv/Icc
Define: Vpsu = voltage at psu terminals

(1) Placing N LEDs in parallel across the psu with no resistors will not damage any LED if current in highest current LED is <= I_LED_max_
(2) Adding resistors can increase light out:

For a load of many LEDs in parallel with no resistors,
Then if Vpsu = Vload  < Vcv (so Iload = Icc)
adding series resistors per LED, but so Vload still < Vcv will increase total light out.
How much depends on several factors - see below.

Let's say we have perfect 5V DC 0.1A power supply.

Assume that means it provides Vout = 5.000...V for Rload >= 50 Ohm = Ioit <= 100 mA.
Also assume it provides 100 mA at whatever voltage suits for Rload < 50 Ohms.

Obviously for one LED we would need a resistor

No. That depends on the LED. If the LED Vf is < 5V at 100 mA it will draw 100 mA at < 5V. If the LED is specified to oprate OK at 100 mA it will be OK.

BUT what if we connect bunch of LED's in series.

Lowest common Vf for visible LEDs is ~~ 2V for red. (Varies widely in special cases).
One LED = 2V
2 in series = 4V
3+ in series = too many
So "bunch" <= 2 for proper operation.

And the current drain is well above the power supply, so voltage on those LED's drops to 2.5-3V.

I assume this means Itotal >> 100 mA if all LEDs operated in "normal" Vf range.
Let's put the bunch of LEDs in parallel to make sense of this
Let's say 20 x 20 mA at 3.2V spec LED's in parallel.

Would you still need to add resistor if LED's voltage is about 3.2V?

No from a ratings point of view.
Maybe from others
If 20 x LEDs rated at 20 mA at 3.2 V were connected to a 100 mA max power supply then they would draw 100 mA. The average current per LED = 100/20 = 5 mA.
If the LEDs are reasonably modern from a reputable manufacturer then, while they will not all draw exactly 5 mA, it is exceedingly unlikely (close to certain) that any will draw over 20 mA when 20 are placed in parallel. So, no LED exceeds its rating.

It might be a silly question, but I thought it'd be cool to not have a resistor in such case (because LED's would be brighter that way)

As above, if the LEDs are in parallel and none exceeds its current rating then they will be safe BUT light per LED will be uneven and light out will porobably NOT be maximised.
Because - LED efficiency in terms of lumen/mA rises as mA falls. The result varies with LED but as a guide 5 to 20% more light per mA may be obtainable at 10% of rated current than at 100% of rate current.
Then, the brighter LEDs make LESS light per mA than the lower brightness LEDs so the ones that "hog" the current make less brightness per current but take a larger share of the current. If the "spread" of currents is small and/or of the efficincy change with current is small then the light output difference will be small. As current rage rises and as efficiency range rises the loss of light due to current hogging rises.
A simplistic worked example shows the likely order of result.
Example - If you have 20 LEDs and the highest current one draws 20 mA, and each less brighter one draws 80.245% of the prior one the the total drain will be 100 mA (actually 99.99936 mA)
ie with I rounded to 0.1 mA LEDS draw 20, 16, 12.8, 10.3, 8.2, 6.6, 5.3, 4.2, 3.4, 2.7, 2.2, 1.7, 1.4, 1.1, 0.9, 0.7, 0.5, 0.4, 0.3, 0.3 mA
A spreadsheet calculation shows that light loss is only about 3%.
ie the loss of light from current hogging is not liable to be vast.
Worse is that the differences can be substantial and very visible.
I have seen lights made with a single common series resistor and 6 x parallel LEDs.
At full power the differences were not visible. At lower powers the differences in brightness were immense.
In the case of a CC supply ADDING per-LED resistors such that V_psu is stil < Vcv, the total LED brightness will INCREASE slightly. This is because power in increases as V rises, LED current is still I_psu_max, VLED rises and so LEDs operate at a more efficient point.
SO
If operating N LEDs from a current limited power supply where Isupply is much greater than N x I_LED_max_rated, then no LED is liable to exceed its rated max current value and no damage will be done.
Answer: as long as you don't exceed the forward voltage rating you wont need a resistor. it will limit the current going through itself, due to power rating. the problem comes from surges and over voltages.
if you stack the LEDs for a 6.4 and so on voltage source what can happen is that one led will short out (melt internally and the magic stops) and then the rest of the LEDs are forced to endure the extra voltage across the junction and they all go bye bye.


Both retired and now want to be snowbirds but have a few of questions?

Question: My wife and I currently live in VA, we are both retired, I have SS and she has CSRS we recently bought a house in Cape Coral Florida. We want to take advantage of the Homestead which will save us $1,000.00 per year in Real Estate Taxes because we plan on being there more than six months out of the year. However we have questions about filing federal and state tax returns.  If my wife becomes a FL resident we can save on state taxes as well from her retirement. This would be more beneficial for us but are concerned that Virginia state may audit because of the value of the property we own in Virginia against my husband social security income?  We own two homes in VA, one is over 1mil in value and the other is rental property.  Can we still file a joint federal return if we claim residence in two different states? What address would we use to file our Federal Return?
Comment: I'm not sure I follow... Why would you claim residency in Virginia? What does home value have to do with it?
Answer: According to the Commonwealth of Virginia Department of Taxation, you're required to file tax return in Virginia if you're either a Virginia resident or have a Virginia source of income.
Home value has nothing to do with it, having a home however does. If you don't convert your Virginia primary residence to a rental while you're in Florida, VA may consider you residents even if you stay in Florida for more than 183 days.

Resident: -- A person who lives in Virginia, or maintains a place of
  abode here, for more than 183 days during the year, or who is a legal
  (domiciliary) resident of the Commonwealth is considered a Virginia
  resident for income tax purposes. Residents file Form 760.

You can still file a joint Federal tax return even if you file separately State because of the residency issues. However I can't see how you would have different residencies. Is the home in VA owned by only one spouse? Even then, VA would claim that it's the place of abode for both of you, making both of you residents...
You might want to read the "Mixed Residency" text on the web page, and see if it applies to you.
Answer: You need to establish residency in another state.
That means make your life revolve around that new state. Register the cars in the new state, and keep them there unless you drive one to the old state when vacationing; register to vote in the new state; have your credit card and other regular correspondence switched to the new state; close your bank account in the old state and open new one in the new state.
Your biggest problem will be the rental property. That will be income generated in the old state. You will have to file a non-resident tax form in the old state because you are generating income there.
Having a home you seldom visit except when vacationing will not make you a resident of the state. Keep records on which dates you are in which state. Don't make it close to being a 50/50 split because one small mistake could cause Virginia to claim you a a resident.
Of course the first year of the switch you will have to file a part year resident form with both states unless the switch happens near the start or the end of the year. Most states ignore a period of less than 1/2 a month of residency.


Letter of recommendation from professor who is not longer at your university

Question: I am applying to graduate school in US for MS and Phd program. I wonder is it a good idea to ask for a letter of recommendation from someone that I took his course and I did amazing in his class and he knows me very well but he is now professor at another prestigious institute ?
Answer: It's not just a good idea, it's an excellent idea.  Your professor is still in just as good a position to speak to his experience with you and his assessment your abilities as he was before.  You say he has moved to another good institution, so there is no reason for his opinion to be discounted just because he moved---changing institutions is not unusual.  In fact, if he is happy to write you a good letter, it will look even better than if he was at the same institution, because even after changing institutions he still remembers you and cares enough to write.
Answer: It doesn't matter where the professor works now, but you should state clearly that the professor once taught you at your university.


Cropping, Re-sizing and Saving images from one folder to another folder in wordpress

Question: I'm adding an upgrade for the WordPress plugin which I have developed ages ago. This plugin is just a product catalog, so just show products and their images. Products can have more than one images.
I was re-sizing images in the older version of the plugin by CSS, assigning them width and height. Which was working but images look stretched but users were happy. Now I have added a new feature in the plugin which is to crop and re-size from the uploaded image and save it with a different name, like a thumbnail.jpg.
The new feature is working remarkably for the new users who upload images, but the thing is about old users who upgraded to newer version.
The issue is old users already has products and images. When I try to get all the products and images via foreach loop, it works perfectly on 200 - 250 images but breaks on more than 250+ images - No Error :(
Many of my old users has 600+ images so I want a way to crop and re-size the existing images and saves them with a new name and save the file names in the DB.
I'm using wordpress's default wp_get_image_editor(); function.
Here's my query to get old products which has images:
$wpc_product_images_sql = "Select wpc_posts.*, wpc_meta.* From " . $wpdb->posts . " As wpc_posts Inner Join " . $wpdb->postmeta . " As wpc_meta On wpc_posts.ID = wpc_meta.post_id Where wpc_meta.meta_key = 'product_images' Order By wpc_posts.post_title;

And here's my foreach loops (I'm using two loops. First one is getting the products which has images and the second loop is for get images from each post, as I'm mentioned earlier in my question that products can have more than one images. So have to use two loops)
foreach ($wpc_images_qry as $wpc_prod_images) {

                echo '
'
                . '
' . $wpc_prod_images->post_title . '
'
                . '
';

                $wpc_post_id = $wpc_prod_images->ID;
                $wpc_product_images = get_post_meta($wpc_post_id, 'product_images', true);

                $big_img_name = array();
                foreach ($wpc_product_images as $wpc_prod_img) {
                    /// For Big
                    $big_resize_img = wp_get_image_editor($wpc_prod_img['product_img']);
                    if (!is_wp_error($big_resize_img)) {
                        $product_big_img = $wpc_prod_img['product_img'];

                        $product_img_explode = explode('/', $product_big_img);
                        $product_img_name = end($product_img_explode);
                        $product_img_name_explode = explode('.', $product_img_name);

                        $product_img_name = $product_img_name_explode[0];
                        $product_img_ext = $product_img_name_explode[1];

                        $big_crop = array('center', 'center');
                        $big_resize_img->resize($wpc_image_width, $wpc_image_height, $big_crop);
                        $big_filename = $big_resize_img->generate_filename('big-' . $wpc_image_width . 'x' . $wpc_image_height, $upload_dir['path'], NULL);
                        $big_resize_img->save($big_filename);

                        $big_img_name[]['wpc_big_img'] = $upload_dir['url'] . '/' . $product_img_name . '-big-' . $wpc_image_width . 'x' . $wpc_image_height . '.' . $product_img_ext;

                        if (file_exists($upload_dir['path'] . '/' . $product_img_name . '-big-' . $wpc_image_width . 'x' . $wpc_image_height . '.' . $product_img_ext)) {

                            echo $upload_dir['path'] . '/' . $product_img_name . '-big-' . $wpc_image_width . 'x' . $wpc_image_height . '.' . $product_img_ext . ' - OK
';

                        } else {
                            echo $upload_dir['path'] . '/' . $product_img_name . '-big-' . $wpc_image_width . 'x' . $wpc_image_height . '.' . $product_img_ext . ' :(
';
                        }
                    }

                }
                update_post_meta($wpc_post_id, 'wpc_big_images', $big_img_name);

                echo '
'
            . '
';
            }

Answer: If I've understood correctly, you just want older images upgraded to be like newer images?
Back up your data first, but if I have understood then just remaking your image sets with a plugin like Regenerate Thumbnails should do the trick.
Test this out on a development copy of your site though!


Find Lat and Long points on land only

Question: I'm new to R and GIS so please forgive me if this is a simple request.
I was looking for a way to find out if a Lat/Long point is on land or ocean. I found this previous post from a couple of years ago which provides an array of true/false results.
Given a Lat and Lon, identify if the point is over land or ocean?
I was able to get it to display the simple world map with the points, but I had two questions:
How do I use the rworldmap with the more detailed and up to date country polygons?
How do I return only the Lat/Long points that are on land?
Basically I am looking to get the Lat/Long points that are on land only and don't know where to start.
Answer: So it turns out it is a single line of code. Using the example in the link, the line of code to only return the lat/long points that are on land is:
pts_land <- pts[c(ii)]
Where pts are all the lat/long points, ii is an array of true/false values and pts_land has all the lat/long points that are on land.

Find Lat and Long points on land only


Why does Ukraine desire EU membership?

Question: On the 28 February 2022, four days after the Russian invasion  had started, Ukraine applied for membership in EU. What were the long and short term causes behind, and the trigger of, Ukraine's resolve to apply for membership in the EU?
Comment: Compare: https://politics.stackexchange.com/questions/71207/what-would-ukraine-gain-by-joining-the-european-union-rapidly/71227#71227 (There are also a lot of other similar questions already.)
Comment: @Stuart F. The two questions are different, but related because they both touch on EU membership. Mine is about the desire to become a member while the other is about the timing of becoming a member. Right?
Comment: Does this answer your question? [What would Ukraine gain by joining the European Union rapidly?](https://politics.stackexchange.com/questions/71207/what-would-ukraine-gain-by-joining-the-european-union-rapidly)
Comment: Yeah the (upon reviewing them) answers to the linked Q are actually a bit one-dimensional as "ain't happening" so perhaps a separate question is worthwhile
Comment: @Fizz. Thx for the suggestion. You must see something I don't. I would be grateful if you could enlighten me with your insight in an answer. It doesn't have to be long. I dislike long answers anyway.
Comment: Wouldn't (as of now anyway) the short term goal be to solidify help against Russia and long term be to have help/assistance in rebuilding? Right now, they've got no solid support for _after_ the war.
Comment: @cGCampbell. Yes. But I believe there is a difference between "goal" and "cause".
Answer: The short-terms one(s) are a bit obvious as (according to polls) the desire of the surveyed Ukrainians to join the EU jumped up dramatically since broad-front invasion by the Russian army has started this year. Basically, once Russia has declared something close to  total on Ukraine, the bridges are burned.
As for the longer terms ones, those are bit more debatable, but if we go by the geographical distribution of the Ukrainian population that does desire to join the EU, which is mostly concentrated in Western Ukraine, Russia taking away in various ways the Russian/Russophile population in Eastern Ukraine in various ways, be it by annexing Crimea or by supporting the self-declared republics of the Donbas, essentially had the same effect of diminishing the pro-Russia population that still lives in areas controlled by Ukraine's government. So in some sense, Russia has been pushing towards the EU the areas of Ukraine they haven't annexed or subverted for quite some time now.
Ukraine itself doesn't have that much of oil/gas-driven economy, so integration with Russia instead is of somewhat questionable benefits. It seems Ukraine mostly exports to Russia aluminium (oxide) and iron products, which I suspect are enabled by imports of cheap energy from Russia. (I don't know how much of that production happens in areas that Russia has already conquered in 2022, but I suspect it's a non-negligible proportion given Azovstal etc.) So while breaking ties with Russia was likely to disrupt those Ukrainian industries, the destruction and occupation brought by the 2022 large-scale war, ironically probably made that easier in the long run. Furthermore, if one takes into account the near complete lack of Russian investments in the reconstruction of a client state like Syria, territories that are aligned with Russia but not 100% physically controlled by it don't seem to fare too well. (Russia did rebuild Chechya, in contrast.)
As for concrete benefits of joining the EU, those are essentially the same that have caused most of Eastern Europe to want to join the EU. Their population eventually gets access to the higher-paying jobs from further West (and in Ukraine's case that probably even includes Poland). That eventually puts pressure of salary growth "back home". It looks like after 2014 more Ukrainians found work in the EU than in Russia, although that might involve some obscuring of the fact that some Ukrainians were incorporated into Russia that year.
The EU also funds development of the poorer areas with their structural funds; the alignment of various standards makes it easier for EU business to expand in the new territories, which generally results in an increased standard of living for most inhabitants, even if there are issue with some industries being pressured out, e.g. coal in Poland... of which Ukraine also has some, but again, I think mainly in the Donbas, so ironically again the Russian (or proxy republics) occupation in that are make the problem "go away" for the rest of Ukraine/EU. Given that Ukraine is a large agricultural producer, which is probably not going to change unless Russia occupies much more of Ukraine than it does now, I suspect EU-membership negotiations on that chapter are not going to be easy though.
Generally speaking however, in the long run, Eastern European countries that have joined the EU have fared better than e.g. Belarus in terms of GDP growth/capita (even at PPP), which has more closely stayed in Russia's orbit. (Somewhat interestingly, Serbia didn't fare that much differently from its neighbors, despite its political flirtations with Russia, but economically Serbia isn't that integrated with Russia, relative to the EU.)
Comment: @alamar The graph of GDP per capita looks quite clear. https://countryeconomy.com/countries/compare/romania/belarus?sc=XE15
Comment: @alamar: I've already said that in my answer. Yeah, technically the EU is only sending that money to low-development/low-income regions (not necessarily countries), but it's a bit obvious where most of those regions [are](https://ec.europa.eu/regional_policy/en/policy/how/improving-investment/lagging_regions/).
Comment: If we compare Belarus with Romania economy devepoment-wise I'm not sure if there would be a clear winner.
Comment: Pre-2014 it looks that Belarus was growing faster. I wonder what would happen if you adjust that by PPP.
Comment: @alamar: I doubt that Ukrainians engage in that much alternative history, i.e. had Russia not been under sanctions since 2014 and had Belarus had not been indirectly affected by those, etc.
Comment: @Fizz They only really had this choice before 2014, and Belarus grew on par with Romania before 2014.
Comment: @alamar N.B. Russia has also been apparently subsidizing the the economy of Belarus to the tune of 10-15% of its GDP, but I only found that stated for 2014; not sure if they could still afford the same level thereafter https://carnegieendowment.org/2014/12/03/revisiting-belarus-reality-beyond-rhetoric-pub-57373
Comment: @Fizz EU has also been subsidizing economies of its Eastern members.
Answer: There are many economical and other similar benefits from being part of the European Union. These are covered well enough in other answers.
While Russia did made economical progress, it is not seen by many as equally great and attractive. It may still be associated with the Soviet Union that was not particularly successful. The belief about the wonderful Europe where the hard work is converted into money and wealth so easily has roots in Soviet times and remains alive maybe because it is not completely groundless, even if at times slightly exaggerated.
Russia could easily fix this problem by achieving good salaries (for the own citizens first), funding joint research programs, getting ahead in advanced technologies. But all this needs money, money, money and money, you must win with the economy first to use such things for boosting the reputation.
Comment: I guess, this answer wants to say that if only Russia would have invested its profits from selling of resources into education, infrastructure and high-tech instead of military or oligarchs, they might be much more advanced by now and maybe even attractive for Ukraine or the EU.
Comment: Yes, this is correct.
Answer: This answer sets out to identify the factors behind Ukraine's desire for full membership in the EU.
The long-term cause behind desired full EU membership would be their sense of identity with Europe, due to geographical location. Everything from the Ural Mountains in the east unto the Atlantic Ocean in the west, and from the Arctic Ocean in the north to the Mediterranean Sea in the south is Europe. 100% of Ukraine lies within these perimeters, in contrast to Russia which is located across both Europe and Asia.
The short-term cause behind desired full EU membership seems to have been the growing economic and social cooperation between Ukraine and EU that gradually emerged after the dissolution of the Soviet Union in 1991. Integration with Europe being a declared big goal in Ukrainian politics already in 1993, according to the linked website.
The trigger for taking the final step and applying for full EU membership, however, obviously was the Russian invasion of Ukraine, which rapidly pushed Ukraine away from Russia into the arms of the EU.
Consequently, major geographical, economic, social, and security factors influenced Ukraine to apply for full EU membership.
Comment: The desire to cooperate with the EU started before the Russian invasion. See [European Union–Ukraine Association Agreement](https://en.wikipedia.org/wiki/European_Union%E2%80%93Ukraine_Association_Agreement). While an association agreement is not yet about becoming a full-fledged member, it's still a step into that direction. There is a reason why the 2014 revolution in Ukraine was nicknamed "[Euro-Maidan](https://en.wikipedia.org/wiki/Revolution_of_Dignity)".
Comment: Maybe Ukrainians themselves said why they desire to be in the EU and corresponding documents could be cited. I'm surprised at an answer that argues from the outside, when it is so easy to just search for reasons within the public opinion of Ukrainians themselves. They should know best. Maybe already before 2022 public opinion was in favor of a EU membership but they didn't really dared to ask for one.
Comment: @Philipp. An excerpt from the link I included in short-term triggers says: "Ukraine's desire to join the European Union dates back to 1993 when the government declared that integration to the EU is the main foreign policy objective".
Comment: @Trilarion. Thx for your thoughts.  It would be really great if you could put together a little answer for me, based on your suggested method.

Why does Ukraine desire EU membership?


Do I have a natural spring or a leak

Question: I live in South Mississippi and have lived in my home with a slab foundation for about 20 years.  I have never had a problem with the foundation and the ground is mostly red clay.  We do have a septic system which was replaced about 2 years ago with an aerobic system that drains into the woods about 50 yards away.  About a month ago I noticed water standing next to the foundation (slab foundation).  I dug around it and it filled up with water.  There is a faucet right there that has leaked at the faucet but I can turn it off enough not to leak.  I've monitored the water meter and there is no leak coming into the house.  I dug a small trench to get the water to run away from the foundation. The water does not smell and looks clean, not cloudy or grayish.  The man with the water company in our community said it is probably a spring and will dry up on its own.  When they installed the new septic system they hit at least 2 other springs in the yard within about 30 feet of this area.  I'm just concerned that maybe the water from the bathroom sink or tub is causing this leak.  They are both right where this water is showing up.  I even took green food dye and put it in water from the sink, bathtub and toilet but nothing showed up outside.  I let the water run yesterday for a while with no change in the water level.  But when I looked this morning the water was up.  Of course I had been digging in the area so that may be why the water has increased.  The water level never gets very high and stays about the same except for this morning.
Comment: Turn main water supply off at street fir 24 hours . If your hole dries up there is s leak. If it continues full there is another source like the under ground spring
Comment: I've taken a picture of the water meter, waited 2 hours and checked and no movement.  I am wondering is there anyway it could be a leak from the bathroom sink or the bathtub?  They are both right near where this appears to be.  I don't think it is the toilet because that goes straight into the septic tank.  Would the drain pipe from the sink and the bathtub also tie in to the line that goes from the toilet?  I guess they would. Of the 2, the sink is closest to the water area. The amount of water I saw this morning could not be just the sink.
Comment: But when you dyed the tub water and sink water you saw nothing it. Is very rare to have toilet and tub/sink draining to separate location. Unless you have a gray water recycling system in place  bottom line if water collects there when you have not used any from your municipal system it is coming from elsewhere
Comment: Yeah.  That's what I thought as I was typing.  I'm thinking more and more it must be a spring just from process of elimination.  It's not the septic tank because there is about 5 feet of dry hard clay between the wet area and the beginning of the septic tank area.  Plus there is no smell.  The real test will be when we leave for a week next month.  Other than someone coming in to feed and water the dogs there will be no activity in the house.  But watch, it will rain the entire week, lol.
Comment: Compare the pH of the waters
Answer: How does the clean water supplied by your utility company differ from natural spring water? Where I live, tap water contains chlorine and chelating agents, and natural spring water contains none of these. Your water company will be able to tell you how to chemically test for tap water vs. spring water.
Comment: The water from the water company comes from springs but they do add chlorine at least to it.  I'll ask the water company guy about testing it.  Thank you.
Comment: Does your water company add fluoride to the water? This is often the easiest way to distinguish ground water from treated water.
Comment: UPDATE The water level is getting higher for some reason. In the past few weeks since I found this it has stayed about the same. But...I did dig a lot around it this weekend trying to make the water run away from the foundation. I think I dug into more spring.
Comment: You might consider sleeping [somewhere else](http://www.cnn.com/2013/03/01/us/florida-sinkhole/index.html) for a while.

Do I have a natural spring or a leak


When is it appropriate to provide clickjacking protection one of my websites pages?

Question: I run a couple of websites, so I'm just wondering what is the appropriate use of clickjacking protection like the x-frame-options response header? What pages are susceptible to this kind of attack on my users?
Answer: In general, every page which allows the user to change data is a potential target for clickjacking. The goal of clickjacking is to trick the victim into taking actions on the attacker's behalf. This affects every page with forms or buttons or other UI elements which have persistent effects.
However, I strongly recommend against taking the blacklist approach and picking individual pages for protection. It's very easy to overlook something, the pages may change over time, and even a seemingly harmless page can become dangerous through an additional vulnerability. For example, the attacker might have found a cross-site scripting vulnerability on your site. By combining this with clickjacking, they may be able to take arbitrary actions regardless of what you originally designed the page for.
The correct approach is whitelisting: You protect every page except those which absolutely must be framed.
Note that setting the header to anything other than DENY isn't reliable. When faced with nested frames, current browsers usually just check the top-level site. This means you can end up with situations like this: You allow the site good.com to embed your page as a frame, but this site also embeds evil.com. This allows evil.com to frame your page despite the X-FRAME-OPTIONS header being set to good.com, because the top-level site is indeed good.com.
So if you do allow framing, expect the page to be framed on any site, not just the one you've chosen.
Comment: Just wanted to add that not all browsers support the X-Frame option. If you're concerned with protecting users with older browsers you need to include frame busting java script on the pages you want to protect.


Will accidentally shaking the mead lower the alcohol percentage?

Question: I shook the mead during fermentation and I'm concerned that i may have hurt the yeast, causing it to produce less alcohol. Could this happen, or am i over thinking it?
Answer: No it wont. In fact it can break up yeast floculation and aid fermentation.
There is risk of oxidation if much alcohol has been produced when it was shook. But the c02 in headspace should minimize it.
I once fermented a 5 gal 1.086 apple wine to 0.992 in a couple days on a stirpate to completely deny the yeast floculation.
Answer: The answer to your question is really dependent on which stage of the fermentation your mead was in.
If it was shaken during the aerobic phase... perfect. The yeast require oxygen to divide cells and prepare for active fermentation.
If the shaking occurred during the rapid/active ferment then you are still OK as shaking here won't destroy any yeast nor will any oxidation have effect. The only time adding oxygen to your mead is bad would be after degassing. It would take quite a bit and deliberate methods as well.
Yeast are durable little guys and there's no way to hurt them short of extreme temps and sanitizing products.
Now as for the whole oxidizing the mead fear is related to you... This would only affect your mead in long term storage life. More than 5-8 years before any results would be noticed.


Language selection for print button

Question: I'm pretty stuck with this one:
I have an explicit 'print' button but we also need to allow users to select the language in which they want the form to be printed. Adding a dropdown next to it before the button feels quite weird. Appreciate your help.
Comment: A dropdown next to the button sounds perfectly reasonable and intuitive to me. If there is a sensible default, you could have a split button with that as the primary action.
Answer: In the app I'm working on, we're introducing a "combo button" that defaults to one command, but, when the arrow is clicked, offers other commands.
The app uses a small "Actions" button that pops up a little panel with commands in it. Functionally similar to the combo button, just visually different.

download bmml source – Wireframes created with Balsamiq Mockups
Comment: Just wanted to make sure. I sometimes feel things look weird when in fact it's just me being weird. Thanks guys.

Language selection for print button


Does inhibiting prolactin levels cause any health problems?

Question: I am using a prolactin inhibitor drug called "Dostinex". In general, it has some positive effects on me (increased libido, better mood) and I haven't realized any bad side effects. I'm wondering, which systems in the body can be affected negatively by low prolactin levels?
Comment: Have you done any research? The list might be long enough to pare down a bit.
Comment: Are you asking about all cases of [hypoprolactinemia](https://en.wikipedia.org/wiki/Hypoprolactinemia), or just drug-induced cases?
Comment: I mean drug-induced
Answer: Prolactin is a peptide hormone that, in addition to modulating the hypothalamic–pituitary–gonadal axis, functions as a cytokine in the immune system and as a growth factor in the vascular system amongst many other functions.
According to Wikipedia:

Prolactin receptors are present in the mammillary glands, ovaries, pituitary glands, heart, lung, thymus, spleen, liver, pancreas, kidney, adrenal gland, uterus, skeletal muscle, skin and areas of the central nervous system.[31]

How prolactin suppresses GnRH, the mechanism through which hyperprolactinemia causes hypogonadism, is unknown. Many of prolactin's other functions may not necessarily be influenced by blood serum levels, as prolactin acts in a paracrine and autocrine, in addition to an endocrine, manner.
The positive outcomes from normalizing hypogonadism should outweigh any negative effects of reducing prolactin levels. Androgen deficiency in males can cause osteoporosis, a series weakening of the bones. Of course, as more is known about the function of elevated prolactin levels, this opinion may change.
Surprisingly, serum prolactin below physiological levels can cause many of the symptoms that high levels can. Prolactin acts as a weak gonadotropin by itself, and enhances the effect of leuteinizing hormone at testosterone-producing cells in males.
Hypoprolactinemia can lead to hypogonadism and osteoporosis, just like in hyperprolactinemia. However, in cases of hyperprolactinemia, cabergoline often does not completely reduce prolactin to normal levels, anyway.
The side effects of cabergoline itself are probably more important. as there are known cases of valvular heart disease in doses used to treat Parkinson's. Inflammation and fibrosis of various tissues can also occur.


Distant retrograde Orbit in CR3BP Question

Question: How can i calculate the initial vy0 component for a distant retrograde orbit in Sun-Earth CR3BP around Earth?
Comment: It seems to me it depends on where you're starting. If starting at aphelion, then v = vh and vy = 0. Ditto perihelion. If r is at 1 A.U. (what I call [medihelion](https://space.stackexchange.com/questions/8782/is-medihelion-a-word), then I believe the vertical component is e * v where e is eccentricity of the orbit.
Answer: One way
is to choose an Earth apoapsis distance, then simply try many of them, where many = thousands or even millions, and see which ones result in something that is close enough to periodic to meet your currently unstated criterion for what would be considered a sufficiently "distant retrograde orbit around Earth".
I believe (someone please correct me if not) that a much faster way would be to use some kind of "shooting method" and converge much more quickly by checking successive tests to see how close to zero vx is at periapsis. vx0 = 0 when x=0 in the rotating synodic frame, so vx a half-period later at periapsis should be at or very close to zero as well.
Shooting Method: (in no particular order)

Chapter 3 in Robert E. Pritchett's Masters Thesis (Purdue) Numerical Methods for Low-Thrust Trajectory Optimization
Single Shooting Handout, Interplanetary Mission Design Spring 2010, Kate Davis.
DESCANSO Book Series; Deep Space Communications and Navigation Series Volume 12, Low-Energy Lunar Trajectory Design Section 2.6.
Quasi-Periodic Orbits of the Restricted Three-Body Problem Made Easy

Another Way
Would be to read all of the really excellent answers to How to best think of the State Transition Matrix, and how to use it to find Halo orbits? and to use them to build a fast algorithm to converge on a periodic orbit.
A Third Way
would be to read up on Planar Lyapunov Orbits and find one that is suitable. This would also require a numerical technique.
A Fourth Way
would be to "go deep" and dig into all the crazy possible CR3BP planar and nearly-planar subsets of the huge variety possible periodic orbits. See for example the papers mentioned below, and also see a sampling of that paper that I show in this answer.
The extremely cool and colorful paper E. J. Doedel et al, (2007) Elemental periodic orbits associated with the libration points in the circular restricted 3-body problem  International Journal of Bifurcation and Chaos 17, 2625 (2007). https://doi.org/10.1142/S0218127407018671 builds a system of illustrations that show all of the known, periodic, orbits in the CR3BP (Circular Restricted Three-Body Problem). This includes many kinds or classes of orbits as shown in the table, but excludes Lissajous Orbits because they are not in general periodic. (note: ignore the drawing in the Wikipedia article!)
You can and probably should also download the paper from its non-paywalled ResearchGate site, make some coffee, then spend six months enjoying it.
There is also an un-paywalled copy of their earlier paper available: The Computation of Periodic Solutions of the 3-Body Problem Using the Numerical Continuation Software AUTO D. J. Dichmann, E. J. Doedel, and R. C. Paffenroth Int. Conf. on Libration Point Orbits and Applications, Aiguablava, Spain, 10-14 June, 2002
Even laptops are gigaflop machines
these days, so this is not as challenging (computationally) as it would be even a decade ago. Of course depending on the method you choose, it can still be mathematically challenging.
So I'd start with the first method.

Write a simple integrator for a 2D implementation of the CR3BP and run it with a bunch of values for vy0 and see what happens!
Stop each one after it passes through x=0
Interpolate to get it's vx at x=0 (what you are trying to zero out)
Make a scatter plot of vx(x=0) versus vy0 and look for zero crossings
Find a way to automate this or converge on the zero
Have fun!
If it doesn't work well, post your results in a New Question. Hopefully with more than one sentence this time, and you'll likely get further assistance. The more details you add to your question about what you've tried, the more willingness there will be to help you solve it.


Hot cocoa settling

Question: My cocoa powder settles in the bottom of the mug when I make hot cocoa using half-and-half (the dairy product). Is there any technique to prevent this?
Comment: You mean to eliminate the insoluble solids, or merely suspend them so you actually drink them?
Answer: Stir!  It's normal :-).  If you want a really smooth suspension, you won't be making it with real cocoa powder, or real dairy.
However I always make a paste with the cocoa and a bit of cold milk while the rest of it is heating up.  That gives the best texture to the final product.  If you don't do that, try it.
Answer: The most effective way would be to not use cocoa powder. If you use an instant cocoa drink, you will get a completely dissolved drink. The downside is that the taste is very different and you can't regulate the sweetness. If you use a bar of chocolate (the process is like making a very thin ganache), you will get much less settling, although you will likely have other cosmetic problems such as some cocoa fat droplets swimming on top. A third option would be to cook a spanish style cocoa drink with starch, which is thicker, but better dispersed.
If you insist on staying with just cocoa in milk, you will never completely prevent settling. Still, you can reduce it. First, make sure that you start it properly, as George M said, by making a paste first. Second, cook it up until you see boil bubbles and then let it cool down, instead of just mixing the powder in the warm milk. Third, use a powerful stirring device, such as a mixer or a blender, that will disperse the powder better and it will need longer to settle. Fourth, do not make it in the cup from which it will be drunk, but pour it slowly into the cup, such that the thick part stays in the vessel in which it was made. The last one combines very well with the cooking up and the mixer suggestions, since you don't want to put your cup on the stove, and a normal cup is usually too full for inserting a mixer's beater inside without splatter.
Answer: I'll settle for cocoa in bottom of mug: Hershey's cocoa powder, sugar and a little warm water to dissolve.  A dash of salt (optional), heat in saucepan until bubbly then add Carnation Evaporated Milk and whole milk.  Heat and enjoy.  The evaporated makes a velvety rich texture.

Hot cocoa settling


What is the difference between astronomy and space stack exchange websites?

Question: I have been going through some questions on astronomy.stackexchange.com and noticed that some questions were merged from space.stackexchange.com and vise versa. My question is simply what is the difference? Would it be a good idea to combine the two websites? If not, why not?
Answer: Space exploration is an enterprise, but Astronomy is a study.
As specifically mentioned in the Space Exploration help center:

Space Exploration is primarily about spacecraft, how to send them to space, and their functions there. Specifically, questions on these topics are encouraged.

Space exploration
Satellite design and operation
Systems with potential use in space
Scientific discoveries made by space probes

Questions these topics (and many others) are not on topic here:

The study of exosolar objects, except as they relate to space travel.
Physical sciences, such as geology, astronomy, meteorology, except as they relate to spacecraft and space exploration.

Here on Astronomy we explain in our help center:

Astronomy Stack Exchange is a Question and Answer site about astronomy and astronomy related topics; the study of objects and matter outside the Earth's atmosphere and of their physical and chemical properties
The purpose of this site is to provide expert level answers to questions on:

Setting up, using and maintaining your astronomy related equipment
Astronomical observations, for all celestial objects across the entire spectral range.
Astrophysics and Cosmology
Planetary Science and Celestial mechanics
Data returned by space missions such as probes, rovers and satellites
What type of equipment will allow you to see a certain entity

What questions are off topic here?

Earth science, unless directly related to phenomena observable on other celestials, Solar system in general of which Earth is a constituent part, or as an origin of observational astronomy where its movement, local and global phenomena might affect observations and measurements in any way, is off-topic on Astronomy but can be asked on Physics now or Geoscience once this Stack Exchange site proposal reaches public beta.
Questions about maintenance and general use-age of equipment such as the Curiosity Rover. A question can be about data returned by these pieces of equipment, such as atmospheric composition and planetary composition, but questions about the tools on the rover or how the rover cleans its solar panel are off-topic
Questions that are purely hypothetical, for example a question such as 'Could a black hole destroy the universe' or 'What if our solar system had two suns'
Questions about artificial satellites whose purpose is not directly related to astronomy. You may ask about their orbit, but not their purpose, use-age and safety features
Questions asking for a specific brand or model of telescope, these are very time and opinion specific and are likely to incite debate

It is important that we have these distinctions because these two areas are separate in the career world as well. They certainly have a large degree of overlap, but Space Exploration has a strong engineering emphasis whereas Astronomy has a strong science emphasis.
Space Exploration has a strong enough following to hold itself as a separate area, and Astronomy is growing a similar base.
Comment: @BakedPotato Actually, beta status around here isn't directly related to production rate. Space Exploration, as I mentioned, is largely an engineering enterprise. Astronomers could care less how the James Webb telescope gets to space; they want to use it for their study. [Space exploration](http://en.wikipedia.org/wiki/Space_exploration) is an enterprise, but [Astronomy](http://en.wikipedia.org/wiki/Astronomy) is a study. Space Exploration is concerned largely with where humans (or their devices) can go. Astronomy is concerned with the science of the cosmos.
Comment: @BakedPotato Wikipedia puts it nicely: "While the study of space is carried out mainly by astronomers with telescopes, the physical exploration of space is conducted both by unmanned robotic probes and human spaceflight."
Comment: Thank you for the detailed response but can you also directly state the difference between Space Exploration and Astronomy? I still don't quite get it or maybe I missed it. I always thought that space exploration was a branch of astronomy. I feel like just because it is two separate career bases is also not a good argument but that could be because I'm not old enough to be looking for a career yet. Also, I have noticed that both sites are in beta so wouldn't the production rate of the two sites increase if they were to merge?
Comment: Thank you for clearing things up for me! I like the part "Space exploration is an enterprise, but Astronomy is a study". You should include that in your actual answer.


Long Stay Visa in Germany

Question: I got selected to an incubator program in Germany and I'm a Sri Lankan citizen. I cannot seem to find the right type of visa I need to apply for. The Embassy told me it has to be Long Term Visa, but there are many categories. Does anyone know what I need to apply for? The program in Germany lasts for 6 months.
Comment: What categories ? I only know that you need a residence permit for a longer stay. You download or get the document from the embassy or mission, explain your reason and your visa is granted (or not). Could you explain in detail what kind of "categories" they are suggesting ?
Comment: Are you sure the visa is the critical point here? You'll need a work permit (probably the EU blue card), which has pretty strict requirements in Germany.
Answer: You will need a working permit (i.e. a blue card). If you are planning to create a startup business in Germany from the incubator, you might have better chances. This requires you however to invest money and create jobs in Germany.
So in any case, you need a "Blue Card". If you cannot claim to be a startup through your investment volume in Germany, you need an income of at least 44,800 euros p/a.
If this is also not possible, I would consult the incubator program directly to inquire how they would recommend the visa to be applied for.
Answer: Why dont apply for a Schengen Visa? Category : Business.
http://www.auswaertiges-amt.de/cae/servlet/contentblob/350388/publicationFile/164910/VisumantragEngl.pdf
They will interview you anyway at the embassy.
See also:
http://www.germany.info/Vertretung/usa/en/05_Legal/
02_Directory_Services/01_Visa/_Permanent_Residence_Visa.html
(cant get the whole link to work)
Comment: Schengen visa is only valid for 90 days, and the "business" category is for business travel, not for actually working and being paid in the visited country.
Comment: Yes. Seems you're right. The blue card you mentioned should be right.

Long Stay Visa in Germany


What CTA color would work best?

Question: I am just getting into UI design. I have a site I am working with right now whose primary color is #ffb606(yellow). All of my CTA's are yellow with white text. I need to change the CTA color but I am not sure if I should go with a more reddish-orange that is in our logo. Or should I choose something completely different?
Any help is appreciated. (screenshots below)
Comment: Hi. Welcome to GDSE. You should show what you have tried.  We have [special requirements for critique questions](https://graphicdesign.meta.stackexchange.com/a/682/89608). Please read them and [edit your question](https://graphicdesign.stackexchange.com/posts/128361/edit) accordingly. Thanks.
Comment: The small version of the logo looks like a sceptical smiley ;)
Comment: From my perspective I think the jumbotron would look better if the team was a silhouette with a gradient. Another issue I am finding is the flow is off with the color combination. Think you need to step back and figure what your front most features are. I would strongly suggest make a site from black and white in HTML than look into adding a color palette.
Answer: All I am going to say is that white text (#FFFFFF) on a light orange-yellow (#FFB62A) button fails the Web Content Accessibility Guidelines (WCAG).
I tested that colour combination on contrastchecker.com, and it fails every single criterion across the board. Choose a different colour instead, and choose a contrasting text colour.

All the red circles with an X are fails.
Note: I have no affiliation with the contrast checker website.
Comment: all good, +1, too
Comment: Why not just post contract checker as an actual URL? I dont see any issues with doing that.
Comment: @Mᴏɴᴋᴇʏ I have done that now.
Answer: For a website CTA you should always consider:

good contrast between button and background
good contrast between button and text
it looks like a button or link

From there it's pretty much up to you what color to use. In my tests usually the specific color doesn't matter, as long as it fits the three criteria above.
In your case, I'd use a completely different color than other elements in the site. Everything is black / white / orange on the screen, so a green or red button would instantly draw more attention to it than the current orange button.

What CTA color would work best?


Preloading an IIR Filter

Question: Is there a mathematical approach to initializing an IIR filter so that turn-on transients are minimized?
Background: I have a high pass Butterworth design that overloads at the start of a sine wave signal.  If I know the sine turns on at phase =0,i.e. at sine(t) = 0, can I preset the filter registers to minimize the overshoot?
Comment: Since you can control the initialization of the IIR, am I right assuming your IIR is a digital filter? May I ask why you chose to use a Butterworth in a digital design? That's not a very common choice.
Comment: it's extremely common for audio heads.
Comment: yes.  and, it's not terribly phase un-linear.  not as good as Bessel filters, but much sharper cutoff than Bessel.
Comment: @robertbristow-johnson ah! Didn't realize that; for the flatness reason?
Answer: This is a common problem, and has an easy solution. The following assumes you are using a cascade of second-order direct-form-1 sections.
 For a Butterworth highpass filter with a small ratio of Fcutoff to Fs, the numerator coefficients are close to [1 -2 1], and therefore the frequency response of the numerator by itself has a large attenuation at low frequencies. This is compensated by the gain of the recursive section (the poles).
When a low-frequency sinusoidal signal is first applied, the input shift register (corresponding to the numerator) is not filled up until the 3rd clock cycle, and therefore the output of the numerator FIR may be large for the first 2 clock cycles, after which it becomes small. These initial large values get captured in the recursive section, and recirculate for some time until they die out.
So the simple solution is to delay the operation of the filter until the input shift register is filled with the first 3 samples.
Comment: Note that this trick is very useful in the case where the input has a DC component that you are trying to remove. Typically you would need to wait quite a long time for the the filter to settle (assuming a high ratio of Fs/Fcutoff). By delaying the filter operation until the input register is filled, the output appears on cycle 3 with no DC component, and no long settling tails.
Comment: Thanks, i'll try this and let you know how it works.  And the DC component is an issue with my application.
Answer: An easy way to deal with this would be to actually let the sine run through your filter for a while, and then just at the right phase save the state of the IIR.
However, chances are: if the impulse response in this situation is a problem to you, your IIR isn't the right design.
Comment: Why so dismissive about discrete Butterworth filters? They have some really nice properties that I've found quite useful for cross-overs and multi-band designs. They can be implemented very efficiently (using all passes) and in particular the phase relationship between high and low pass are very useful.
Comment: not really dismissive! I'm just skeptical when someone uses an IIR but doesn't want typical IIR properties (like the reaction to the wideband excitation through the beginning of the sine).

Preloading an IIR Filter


Night pictures lights superimposed to a second location?

Question: I have a DSLR and when I take photos at night or in low light I have noticed bright spots will be seen a second time somewhere else in the picture.  Almost like a reflection within the picture itself.  I first noticed it when taking pictures of the moon.  How do I stop this?
Comment: There are some comments to this answer to another *ghosting* question that offer suggestions for dealing with ghosting.    http://photo.stackexchange.com/q/35052/15871
Comment: Thank you Michael I didn't know it was called ghosting.
Answer: That's exactly what the problem is, internal reflections within the lens due to a high-contrast scene (the light value of the candles will be many, many times greater than the rest of the scene). This can be challenging even for some expensive lenses.
Reducing the scene contrast by increasing ambient light is one answer, either by increasing existing light or using an external flash with a movable/bounce head, so you can boost the ambient light by bouncing the flash off the ceiling (or a portable reflector etc.)
Stopping down the aperture may also help reduce the internal reflections, but reducing the scene contrast with increased ambient light will help more as you're already working in a low-light situation - stopping down will impact on the shutter speed, not helpful if any of your subjects are likely to move.
Answer:
Remove any filters screwed onto the front of your lens. The flat rear surface of the filter is perfect for creating reflections of light bouncing off elements in the lens, or even from the sensor stack itself.
Use a lens with better anti-reflective coatings or a camera with a less reflective sensor/filter stack.
Try to compose shots so that the brightest points in your scene have bright visual elements at the corresponding point in the cross quadrant to make the reflection less obvious.
Make a mask for the front of your lens that blocks half the field of view. Then combine two exposures, one with the mask on the left, the other with the mask on the right (or you might do the same thing with a strong graduated Neutral Density filter). The reflections would still show on the "dark side", but you would mask them out in post processing when combining the two images.
Answer: You might try a different lens. The coatings on camera lenses are there to reduce internal reflections. A different lens may give you better (or worse) results.


Database of self-inflicted injuries?

Question: I need a database of self-inflicted injuries, their prevalence, age, gender and area distribution and the nature of the injury. This is very specific but could have a huge impact in my research. Any help would be very much appreciated.
Comment: WISQARS? http://www.cdc.gov/injury/wisqars/
Answer: Sounds like very interesting research.
There is a database of self-inflicted injuries and suicide from the U.S. Centers for Disease Control and Prevention.  Faststats has both summary and detailed information about this.  There is a related set of data on unintentional injuries that may also be helpful.
Answer: You can use the National Electronic Injury Surveillance System (NEISS)

Date (one year maximum range; e.g., how many injuries were treated in 1996)
Product (e.g., how many bicycle injuries occurred)
Sex (e.g., how many injuries occurred to women)
Age (e.g., how many injuries occurred to people aged 35-55)
Diagnosis (e.g., how many lacerations occurred)
Disposition (e.g., how many people were admitted to the hospital)
Locale (e.g., how many injuries occurred at a school)
Body part (e.g., how many injuries involved the knee)

Here is the link to the Query Tool
(source: QZ, and their twitter-bot)

Database of self-inflicted injuries?


Why does Bitfinex allow shorting with BTC as collateral?

Question: I made a mistake today where I shorted BTC on Bitfinex using BTC as collateral. Why is this even possible, I cant figure out why someone would want to do that?
Answer: Shorting is normal trading transaction on real financial markets. Without shorting you would not be able to speculate and profit on price decline. Assume that btc price is 400 USD and you think that the price will go down. By shorting one bitcoin you simply borrow one bitcoin from some lender and sell the bitcoin for 400 USD. If your assumption is correct and price goes down, say to 100 USD, you buy that bitcoin back and return it to the lender. Your profit then is 400 - 100 = 300 USD.
Comment: Yes, that's how shorting works.  The question is why it makes sense to pledge your own bitcoin (instead of dollars or something else) as collateral for the bitcoin you are borrowing.  On the face of it, this would seem like a no-op.
Comment: Shorting always includes borrowing some of the bitcoins on the top of those you sold, meaning that you sell your bitcoins and broker always sells some more bitcoins borrowed from the lender, typical ratio is 1:4, one btc ours, 4 btc from the lender. Selling bitcoins without lending bitcoins is not shorting, it only protects your portfolio from loosing its value, but does not generate profit.
Answer: In well regulated markets (Bitfinex's aim) traders should have the ability to profit from movements in both directions.
Shorting also assists in the formation of price bottoms. The only way a short seller can capitalize after a down move is by buying back the shorted BTC. This has the net effect of creating buyers after a down move which helps bouy the BTC price.
Bitfinex can also adjust its overall risk and generate some additional revenue by lending out BTC's to short sellers.
Comment: I know what shorting is, the question is about the collateral.
Comment: By using BTC as collateral instead of USD,EUR etc you can mitigate some of the exchange rate risk.


schematic for battery and solar cell in parallel

Question: I have a thermometer, that the sender uses 2 batteries AA (2 x 1.2V). I would like to add a solar cell to use it to load the battery. I tried to connect both (battery and solar cell in parallel) with a diode in front solar cell to avoid any reverse current into the solar cell. Somehow it didn't work, it means, the thermometer stopped to send information to the base. As soon as i removed the solar cell, it started back to send information to the base. so I would like to ask if there is any schematics that I can use as example.
Comment: I don't have the expertise to really summarize this **well** and I'm not just going to drop a link in an answer - but there's a lot information here - http://www.robotroom.com/Solar-Recharging.html
Comment: What nominal voltage/wattage is your solar panel? How much current (roughly) does the thermometer draw? If you have the Model number or specs for it this would be useful. Also, what exactly do you mean by "didn't work" - did it fail to turn on at all or...?
Comment: Please provide a schematic of what YOU have done. What you describe sounds like it should work so you need to draw out what you are doing. PV (= photovoltaic = solar cell) voltage MUST be > battery voltage to charghe. Is it? Charging miusgt be done in sunlight - inside light has almost zero energy. Where is the PV panel you are charging the battery??
Comment: @rfusca It's almost what I want, but wouldn't be easier to just use the solar cell to load the battery and use the whole time the battery as power source?
Comment: See additions to my answer.
Answer: Please explain what you mean by didn't work.
 With no rudeness intended - the connection is simple enough that supplying a diagtram is still no guarantee it will "work" - see below. You appear to have all the parts and appear to have connected them correctly. As it does not work and should, the answer consists of finding out what is wrong.
Please provide a schematic of what YOU have done.
 What you describe sounds like it should work if you have done as you said so your equipment may be wrong or you may be doing something wrong.
ng.
Charging MUST be done in sunlight  or direct daylight
 Inside light has almost zero energy.
 Where is the PV panel located when you are charging the battery??
PV cell  (= photovoltaic = solar cell) voltage MUST be > 2 x AA battery voltage to charge. Using voltmeter place panel UNLOADED in direct daylight
 Is it?
 For 2 x AA NimH VPV must be > ~= 3.5V unloaded and more ios betterFor 2 x Alkaline AA for Vpv to take over from batteries Vpv unloaded needs to be 4V+ and more is better.

Solar cell addition  sanity check
Adding the solar cell to the system when it is running from batteries should either
 -  Provide extra energy from the solar cell or
 -  Do nothing
 Stopping it working is not an option ! ;-).
 If it DOES stop it working and the two x AA batteries are still there then the diode is reversed or faulty.
NimH batteries are about 1.2V nominal when working but are say 1.3V when fully charged AND need up to 1.45V per cell in charge mode to fully charge them.
 If a Schottky diode is used it will drop about 0.3V. It a silicon diode is used it will drop about 0.6v.
 So 2 x NimH + Schottky diode need about 1.45 + 1.45 + 0.3 = 3.2V
 That's loaded. Open circuit voltage will be about 1/3 higher = say 4.2V if you want full charging current when battery is almost charged.  My suggested 3.5V minimum was a compromise - with more being better.

To get some idea of PV panel performance

Place in bright daylight on a sunny cloudless day - ideally pointing at the sun at midday.
Measure unloaded voltage = Voc.
Short panel with an ammeter (multimeter on say 200 mA range).
Measure short circuit current = Isc.

Actual achievable power will be ABOUT Vpp x Isc x 0.5
Comment: as usual you are always helpful :-)
what I mean with "it doesn't work". With the solar cell, the sender didn't communicate with the base. I removed the solar cell and it worked, it means it sent the temperature to the base. I will check in the sun how much voltage my cell is able to provide. BTW a rechargeable battery (AA) here (Germany) has something around 1.2V. So my cell should generate ~= 2.4V, right?
Answer: Using a solar cell to charge batteries used to be done like that in the old days, but nowadays we use charge regulators (not necessdarily expensive). There are a few problems with your approach :

The voltage of a solar panel is not constant.
The voltage of the battery will prevent optimal performance of the solar cell.
The voltage of your battery will be different under load and when charging.

If you want to avoid using a regulator, you are going to need to get your multimeter out and check things are like they should be.
What is the charging voltage of the battery? The charging voltage and the operating voltage of the battery are not the same. If you are running your solar panel in parallel to your battery in parallel to your load, can your load handle the voltage difference? A charge controller will give you a (more or less) constant voltage reference.
What is the open-circuit voltage of the solar panel? You say you are measuring temperature, is it a particularly hot environment? If so, you'll need to check the voltage at the operating temperature of the solar panel. Even so the voltage of your solar cell will change as a function of light intensity and temperature.
What is the voltage drop across your diode? Your solar panel will operate at the charging voltage of the battery plus the diode voltage, about 14.6 V. You need to check that you are getting reasonable current out of your solar panel at this voltage, given temperature and light intensity. For reference check your manufacturer data sheet for a graph similar to this.
If you are confident that your solar panel is the right size for your battery you will need to connect the positive terminal of the solar panel to the positive terminal of the battery, with the diode preventing current from entering the positive terminal of the solar panel. The most reliable solution though is to buy a charge controller.


Flea eggs or dander?

Question:
Are these white spots in my cats brushed fur flea eggs or dander?
Answer: It is not possible to say from your picture so to be sure you need to bring your cat to a vet for a diagnosis and treatment.
It might be lice too,A quick way to see if it is is to hold your hand at one point on the back of your cat for a couple of minutes,This will atract the lice so you will be able to see it crawling in the fur of your cat.
You will still have to visit your vet to be sure,Cat lice if this is what it is can not live on people but if you have other cats they needs to be treated at the same time to get rid of the problem.
This answer is only one of several things it might be so i might be wrong on this one.
If you take the cat to the vet,Your vet will look at this in a microscope and be able to tell you what it is and recoment a treatment if it is lice or if it is dander.

Flea eggs or dander?