Short answer - yes.If you have a single-pane window, light that doesn't reflect off the front or rear surface will be transmitted. But a second pane might once again reflect some of this light, and that has a chance of making it all the way out to the front. The second pane doesn't "stop" any of the reflection off the first pane - so it can only add to the total reflection.
Here is a diagram that demonstrates this:Reflections A and B will happen with just a single pane; C and D are added with a second pane, and you can keep going.Calculating the theoretical total reflection is not too hard. Assuming normal incidence, the Fresnel reflection equations tell us the reflected intensity is$$r left|fracn_1-n_2n_1n_2right|^2$$From the symmetry of this equation you can see that the reflection off the back surface is the same as the reflection off the front surface - but then that ray (marked B) needs to be transmitted - where of course $t 1-r$. This means that the intensity of AB is given by $rt^2r$ (A is just reflected, while B undergoes transmission twice and reflection once). For C, there are 4 transmissions and one reflection; for D, it is 6, etc. Thus, for a stack of N window panes, the reflected intensity (if there is no absorption, and light is too incoherent for interference effects to be significant), the reflected intensity is$$I r sum_i0^2N-1 t^2i$$This is a geometrical series that sums to$$I fracr(1-t^4N)1-t^2$$It is clear from this equation that as $N$ gets bigger, the reflected intensity also gets bigger - although it's a law of diminishing returns. We can plug in some numbers.
..For a typical case of glass with n1.
5, we get $r0.
04$ and $t0.
96$, so the fraction of reflected intensity for a single pane (AB) would be $0.04cdot(10.96^2) 0.077$; a second pane would bring the fraction up to 0.142, and an infinite stack would give a reflected fraction of 0.
510Peripherally related is this question and associated answer
------2. Hedera Helix leaves developing brown spots
Hedera can develop these symptoms if it's in a situation that's too hot, especially if it's hot at night too. Given the heatwave in Europe, you're obviously not currently in control of air temperature, but because it's been so hot, check the plant thoroughly for spider mite - look under the leaves, at the leaf petioles and all the branches too. Spider mite can be an issue if temperatures are high, so you may need to use a treatment for that if it is present.In regard to watering, water when the surface of the soil in the pot feels just slightly dry to the touch - water thoroughly and empty out any excess from the outer pot after 30 minutes. These plants should be kept well watered during spring and summer, and misting regularly is a good idea, especially in winter if the room is kept heated. Lastly, Hedera is resilient; a few blotchy or dried leaves here and there is not really an issue, so long as the roots and most of the plant is okay. Any particularly affected stems can be cut off and the plant will respond by putting out new growth. Hedera kept as houseplants should be trimmed back periodically to keep the plant bushy anyway.In terms of light, they do appreciate bright daylight during spring and summer particularly, but not sunlight, although sun in the winter through a window is fine. UPDATERe spider mites - they can be difficult to shift, but you can use a homemade remedy made with insecticidal soap or 'eco' dishwashing fluid (not detergent based) and water, mixed together in a spray, see here for instructionsyou can use a contact insecticide - this linkis obviously a UK one, but the information is still valid - check what products you have available where you are. Note that biological controls aren't ideal for your circumstances, they work best in glasshouses or conservatories full of plants. Misting regularly will help - spider mites like hot/warm and dry conditions.
------3. Can I dynamically call a LGPL/GPL software in my closed-source application?
This answer was originally posted by Josh Kelley at StackOverflow (second link might be visible to 10k only), but was removed there due to being off-topic. It has been preserved here in light of this Meta StackOverflow request. Linking has a specific meaning in computer programming. You're not linking GPL'ed or LGPL'ed code at all, you're only spawning a GPL'ed or LGPL'ed binary, and the GPL and LGPL permit this. Your users are free to use that binary themselves for its authors' intended purposes and are free to download and compile the source themselves, so all of their freedoms are preserved, and you're not in violation of the GPL or LGPL. (This is what the GPL FAQ is talking about by "communicating at arms length.
") This doesn't even violate the spirit of the LGPL and GPL; they tolerate the existence of proprietary software and assume that at some point proprietary programs will spawn free programs and vice versa. (Otherwise, we couldn't run any GPL'ed software under Windows.)The GPL does require that proprietary and GPL'ed programs "are not combined in a way that would make them effectively a single program.
" If your program is completely dependent upon GPL'ed executables, such that it wouldn't be usable without them even though it is a standalone binary, then that might place you on shakier ground. (And it's probably time to consult your lawyer to find out for sure.)Also, although you didn't specifically ask about this, keep in mind that distributing GPL'ed or LGPL'ed software with your software means that you're required to include a copy of the license with your installer and to also distribute the source code. For example, if you package up your application in an installer and include copies of GPL'ed or LGPL'ed executables in the installer, then you're distributing LGPL'ed or GPL'ed code and must make copies of the source code available (either online, by mail-in offer, or by CD, depending on how you distribute your app). Including a link to the upstream project is not sufficient (at least for version 2 of the GPL). Read the GPL and LGPL for exact details
------4. How do you set up PhysFS for use in a game? closed
You want to know how to compile and link against PhysFS. First, you need to create the binaries to link against. I'll assume you're using MinGW with C::B.
Unzip your PhysFS archive into a directory (e.g. C:physfs-2.0.2)You want to download CMake as per INSTALL.TXT in the directory. Once installed, open the CMake GUI and point the first field (Where is the source code:) at your directory (C:/physfs-2.
Create a directory for the binaries (doesn't matter where, I created one on the desktop) and point the second field (Where to build the binaries:) at that.Click "Generate". Under the drop-down for generators, I chose "CodeBlocks - MinGW Makefiles" - assuming you're using CodeBlocks with MinGW and MinGW is installed to its default location, this will work. Otherwise, you'll have to click "Configure" and play with the settings.
Assuming no errors, navigate to your directory and open PhysicsFS.cbp. Try to build it - chances are, you'll get an error about an unused variable. If you do, expand the virtual folder "CMake Files" in the project file structure and open "CMakeLists.
On line 47, remove '-Werror' from ADD_DEFINITIONS(). Try to build the project again - this time, it should work. You now have files in your project directory: libphysfs.
a. Create a folder for your binaries, e.
2bin" and copy them there.
In the Code::Blocks settings, you need to now add "C:physfs-2.0.2" as a compiler search directory and "C:physfs-2.0.2bin" as a linker search directory. This can be done either locally to the project or globally to the IDE, depending on your needs.
Finally, right click on your project, choose "build options", go to "linker settings" and under "other linker options" add -llibphysfs at the end.Now, in your project where you want to use PhysFS, make sure to #include physfs.h, but don't actually put the file (or any of the physfs files) in your project.
Try building your project and (assuming there are no errors in your code) it should compile
------5. Should I expose my Active Directory to the public Internet for remote users?
Ewwhite,Your question is extremely valid and deserves a careful review. All security professionals recommend layers of security in front of any network resource, including SPI Firewalls, IDS, Host Based Firewalls, etc. You should always use a proxy perimeter gateway firewall like ISA (now TMG) when possible. That said, Microsoft Active Directory 2003 has had no major vulnerabilities disclosed publicly. LDAP technology and it's hash algorithms are generally very secure. It's arguably more secure than the SSL VPN if that SSL VPN runs OpenSSL and is vulnerable to heartbleed. I would caution 5 things:Be concerned about the other services that face the network such as Terminal Server, DNS Services, CIFS, and especially IIS with its terrible security record.Use LDAPS with a security certificate to avoid passing clear text domain credentials over the wire. This happens automatically after installing Certificate Services (use a separate machine for PKI)Put a packet sniffer on the interface and watch your traffic, correct any clear text passwords because firewall or not, if your not using a VPN or LDAPS, some legacy systems will send clear text passwords.
Know that MITM attacks can force the native authentication mechanisms to downgrade and expose passwords to weaker NTLM authentication. Be aware of some user enumeration vulnerabilities that may still exist. That said, Active Directory has a great track record for security. Further, MS Active Directory doesn't store passwords, only hashes which may also mitigate the severity of a compromise. You may benefit from a more seamless security infrastructure, you don't have to set special DNS servers or use domain.local and you can use your actual domain on the public internet such as domain.
com. In my professional opinion there's a substantial benefit to deploying security technologies like Active Directory publicly, where other technologies like Exchange and DNS and Web Servers simply provide no benefit and all the risk.Note: if you deploy Active Directory it will include a DNS server. Be CERTAIN to disable recursion on your DNS servers (enabled by default) or you will absolutely be participating in denial of service attacks. Cheers,-Brian.
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