text:
Talk:Active noise control

Reference 2 needs a citation itself
It is used as a citation without any real citation. — Preceding unsigned comment added by 78.162.232.188 (talk) 14:29, 25 January 2020 (UTC)

Phase vs. polarity
Inverting polarity and shifting phase by 180° are not the same thing. Shifting the phase takes one cycle's worth of time. Inverting polarity is instantaneous.

--Paclopes (talk) 01:21, 4 May 2009 (UTC) Polarity usually refers to the polarity of ligth haves, that are described by a time varying vector field. Sound haves have no polarity. They can be described simply by the variations from the atmopheric pressure level at a given point. I am goingo to remove the references to polarity from the text.

Ideally, the noise cancellation device flips the polarity of the wave to cancel the noise. This would be the case in noise-cancelling headphones, for instance, where the electric wave can easily start from the microphone, be flipped, and travel to the speaker just in time for the acoustic wavefront to get there.

I left the phase comment in place because I imagine there are other systems where you might actually want a phase shift, if there is some kind of unavoidable delay in the system or something? But maybe it should be changed to polarity, too. - Omegatron 16:41, Apr 15, 2005 (UTC)

 * That depends on how you implement the phase shifting. If you're doing things digitally, you're breaking down signals into time-independent channels when you do the Fourier transform, so phase and polarity changes are identical. A more accurate description would be to simply say that the system computes a sound to generate that causes destructive interference (cancellation) at the desired location. To call this "reversing polarity" or imposing a "180 degree phase shift" is to grossly oversimplify, as you have to take into account the positions of your cancelling speakers, microphones, and desired silence zones (sound propagation causes a different phase shift in each spectral component, due to finite speed of sound). --Christopher Thomas 23:22, 28 August 2006 (UTC)

 * You wouldn't do a Fourier transform if you were just going to flip the polarity. :-)  I agree that it should just state what is going on in general at first, as I'm sure different systems have different implementations.  Some just flip the polarity, some incorporate a time delay, some incorporate filtering, variable phase shift across the frequency bands, etc. — Omegatron 23:39, 28 August 2006 (UTC)

 * I have trouble seeing how any system that didn't work in the frequency domain would work in practice. Something that simply generated a signal with negative amplitude would have have the microphone and the speaker in the same place, which would also have to be right on top of either the noise source or the person who you wanted to insulate from the noise. Even if you're willing to do this, something like a noise-cancelling headphone set would have to use a band-pass filter to allow desired sounds to pass, and for both at-source and at-listener versions you'd have to perform strange tricks to avoid feedback problems (trying to cancel the cancellation signal).

 * Lastly, a stronger argument occurs to me (which has apparently been stated by others in subsequent threads): Flipping the polarity of the waveform does, in fact, produce a 180 degree phase shift (at least if you're using a sampling window small enough that sound isn't changing much over the window). You've apparently argued below that the mechanism is different, but that assumes a very narrow definition of phase shift (i.e., the operation performed by a causal phase-shifting filter, rather than the phase shift itself). In both engineering and mathematics, the term typically refers to the result only, without requiring the operation to be causal (which is what gives you a delay when implementing a phase-shift filter). --Christopher Thomas 00:36, 29 August 2006 (UTC)

 * I have trouble seeing how any system that didn't work in the frequency domain would work in practice.
 * Not as well. :-)  But it would still work.  As long as the noise level is lower with the device on than off, it's working.  Obviously some implementations work better than others.
 * In both engineering and mathematics, the term typically refers to the result only, without requiring the operation to be causal (which is what gives you a delay when implementing a phase-shift filter).
 * Exactly. An active noise control is inherently causal. — Omegatron 02:29, 29 August 2006 (UTC)

 * If you are agreeing with my last paragraph, then why are you arguing that "phase shift of 180 degrees" is not correct? If you are disagreeing, please state what parts you disagree with. As-is, your statement appears both confusing and incorrect to engineers and mathematicians for the reasons stated above.--Christopher Thomas 02:54, 29 August 2006 (UTC)

 * I don't understand what you're asking. — Omegatron 03:07, 29 August 2006 (UTC)

 * Capsule summary of this thread as I've been interpreting it:

 * O: Inverting polarity and shifting phase by 180° are not the same thing.

 * C: Yes they are, for reasons X, Y, and Z, and saying they're not confuses scientists and engineers.

 * O: I agree with your statements, but you're still wrong.

 * C: Come again?

 * My apologies if I'm missing something you've said, or haven't expressed my own statements clearly enough, but that's pretty much how I'm presently parsing this conversation. --Christopher Thomas 03:22, 29 August 2006 (UTC)

Let me try and summarize/summarise:

 * At the exact point in space where noise cancellation is actually taking place, the antinoise waveform is polarity flipped from the noise waveform, thus causing destructive interference.

 * At that same point in space, the antinoise waveform (taken as a whole) is not phase-shifted 180 degrees from the noise waveform; this would not cause destructive interference.

 * But if you could take the Fourier transforms of both the noise and antinoise waveforms, you'd find that each individual sine wave component within the antinoise waveform is both polarity-flipped and 180 degrees opposite in phase from its corresponding sine wave component in the noise waveform. This is because, for the specific case of a sine wave, there's no distinguishment between being "polarity flipped" and 180 degrees phase shifted.

Everyone: have I sumari[zs]ed this correctly?

Atlant 13:04, 29 August 2006 (UTC)

 * Pretty much. To rephrase my complaints:
 * The term "phase shifting a signal" is ambiguous, as it could mean "delaying a repeating (or short-time stationary) signal by a fraction of its fundamental frequency" or "delaying each frequency component individually by an equal fraction of a cycle", which have completely different effects:
 * Delaying an entire wave by a fraction of its cycle can be used for noise cancellation (as described in the first section of the first patent of such a system)
 * Phase shifting each frequency component by any value other than 180° would not be as useful (unless the medium is dispersive?)
 * I think that using the term "phase shifting" is highly misleading, when the actual electronics merely flip the wave. I'm aware that the output waveforms are mathematically equivalent in a non-causal theoretical treatment, but the actual device is just flipping the signal over, and it's misleading to imply otherwise.  It's not doing an analog-to-digital conversion, applying an FFT, shifting the phase of each component, inverse transforming, and doing a digital-to-analog conversion.  It's not applying an all-pass filter with a constant phase shift for each frequency, set to 180°.  (Both of which would require a time delay.)  It's just flipping the black and the red wires. — Omegatron 13:55, 29 August 2006 (UTC)

 * This appears to summarize things, but I feel strongly that saying that "inverting polarity and shifting phase by 180° are not the same thing" is at least as misleading, because for us signal-processing types, phase shifting is usually interpreted as referring to each of the component frequencies.

 * Would a phrasing along the lines of, "...implemented by inverting the polarity of the waveform, which has the effect of altering the phase of each frequency component by 180 degrees, causing destructive interference" be acceptable to you? It would certainly go a long way towards eliminating my concerns (and apparently the concerns of other responders), while hopefully avoiding the ambiguity which you're objecting to. --Christopher Thomas 02:18, 31 August 2006 (UTC)

because for us signal-processing types, phase shifting is usually interpreted as referring to each of the component frequencies.
 * That's simply not true. Terms like "phase shift" are ambiguous when talking about anything except sinusoids.  Most of the time, they are actually interpreted to refer to the cycles of a repeating waveform as a whole; not the individual frequency components, though both meanings are valid:

 * Phase shift : A change in phase of a periodic signal with respect to another periodic signal or reference signal.
 * Phase : A time based relationship between a periodic function and a reference. In electricity, it is expressed in angular degrees to describe the voltage or current relationship of two alternating waveforms.
 * Phase Difference : The time expressed in degrees between the same reference point on two periodic waveforms.
 * Phase : A particular angular stage or point of advancement in a cycle; the fractional part of the angular period through which the wave has advanced, measured from the phase reference.
 * Phase Shift : The angular difference of two periodic functions.
 * Phase : The timing of a sound wave that is measured in degrees from 0-360.
 * Phase Shift : Frequency interaction ... which can cause some frequencies to be delayed with respect to other frequencies.
 * phase shift : The change in phase of a periodic signal with respect to a reference.
 * phase difference : The time interval or phase angle by which one wave leads or lags another.
 * Besides, even if it does have a well-defined meaning in a certain field, Wikipedia is not field-specific, so we can't just say it has one particular meaning when it has a variety of meanings in general usage.

''Would a phrasing along the lines of, "...implemented by inverting the polarity of the waveform, which has the effect of altering the phase of each frequency component by 180 degrees, causing destructive interference" be acceptable to you? ''
 * Not really. To reiterate:
 * I'm very well aware that $$\sin(\omega t) + (-\sin(\omega t)) = \sin(\omega t) + \sin(\omega t + \pi) = 0$$. Really.  They are mathematically equal.  I know this.
 * For a non-sinusoidal signal, a polarity flip is mathematically equivalent to shifting each individual frequency component by 180 degrees. Yes, I know.
 * But you could also say $$\sin(\omega t) + \sin(-\omega t) = 0$$. No one is calling it "time-reversal cancellation".  You could say $$\sin(t) + \int { \int { \sin(t)\,dt }\,dt } = 0$$, but no one is implementing a circuit with double integrators to achieve the same result as an inverter.  It is misleading to say you are phase canceling when you are really polarity canceling.  Yes, the outputs are indistinguishable, but the method is not.

 * Also, in real, practical systems, the method used will never achieve ideal mathematical results, anyway, so you will only have partial cancellation, and the methods used will be distinguishable. $$\sin(\omega t) + (-0.99 \sin(\omega t)) \neq \sin(\omega t) + \sin(\omega t + 0.99 \pi)$$

 * Also, different physical devices use different methods with varying degrees of cancellation. The simplest, and most well-known, is to just invert the polarity (which certainly does not require performing a Fourier transform, as you seemed to imply above), but there are more advanced methods with better results.  We need to document this in detail.  So in the intro, we just say "...implemented by generating a wave that causes destructive interference".  Later, we say "The simplest and most well-known method is to invert the polarity, which cancels out waves adequately in certain conditions, such as plane waves in ducts or localized low frequency..."  "A more complex method uses adaptive filters to... " and detail each type.

 * "How can I create a simple sound cancellation device?" and the Active Noise Control FAQ contain information that we should cover here. — Omegatron 16:55, 5 September 2006 (UTC)

Comments to phase vs. polarity
ANC systems actually use both polarity inversions and phase shifting, depending on the controller strategy. There are two types of control strategies: feedback and feedforward.

- In a feedback control system, the signal you want to cancel (error signal) is fed to the controller. Commonly, a polarity inversion and some filtering are used, which may cause phase shifting. This type of strategy is the simplest one, but can only be used when the delays between the speaker and the error microphone are small; otherwise the system becomes unstable. Also, when using feedback controllers, it's not possible to cancel in the whole frecuency range, in fact there are always amplifications in some frequency bands. It can be done using analog devices.

- In a feedforward control system, a reference signal and the error signal are fed to the controller. The reference signal is correlated with the sound you want to cancel; in other words, it gives the controller information about the signal it has to cancel. The controller then uses a minimization algorithm to compute the appropriate filter so that the filtered reference signal emitted trough the speaker minimizes the error signal. In this case filters are used, which shift the phase of the reference signal. It is possible to obtain cancellation in a frequency range without causing amplifications in other bands. This strategy needs complex calculations, so a DSP or other computer system are required.

In any case, when defining the concept of destructive interference, the signals have opposite phase in a mathematical sense, regardless of how you obtain that difference of phase in practise, by inverting polarity or shifting the phase. --Alejandroff 11:50, 19 October 2005 (UTC)

 * This paper defines them differently. It says feed-forward is for canceling a repeating signal that is already well-known, and feed-back is for canceling unpredictable noise from the environment. — Omegatron 14:04, 5 September 2006 (UTC)

 * If you are talking about the small description in (Rafaely and Jones 2002), that is just talking about what they did in the experiment, which was about headsets. Talking in general, it is clear that with a feedback controler you can only obtain sound reduction in a certain frequency range. The width of this range will depend mainly on the delay between the error microphone adn the secondary speaker. In a headset, this delay is obiously small, but in almost all other application of ANC, this is not the case.

 * Feedforward controllers only need a reference signal, in other words, you need a signal correlated to the noise you want to cancel. All you need is that reference signal, you don't need it to be periodic, it can be white noise, for example. The band you can control is basically the band of the reference signal; that is, if the reference signal has power in one frequency band, in principle you can obtain canelation. this article refered here, in which i particiapted, discribes an example of broadband noise cancelation of a white noise signal using a feedforward controller.

 * Nelson, P. A. and Elliott, S. J., 1992. Active Control of Sound. Academic, London.
 * Elliott, S. J., 2001. Signal Processing for Active Control. Academic Press.
 * Kuo, S. M., and Morgan, D. R., 1996. Active noise control systems. John Wiley & Sons, Inc.

 * Those references are good books that explain all this methods deeply. — Alejandroff 02:22, 5 November 2006 (UTC)

More on phase versus polarity
I've just removed the several comments in the article that incorrectly stated that the antinoise signal was not a phase-reversed version of the noise. I suspect the problem was that these statements were phrased too simply to be meaningful, but it's easily shown using the Fourier transform that, for those frequency bands where noise cancellation is taking place, the various frequency components of (that is, the multiple sine waves that constitute) the antinoise signal are most definitely phase-reversed from their analagous components in the noise signal; that's why destructive interference takes place. In the time domain, the antinoise is polarity reversed. In the frequency domain, it's phase-reversed (which, for a sine wave, also happens to be polarity-reversed, frequency-by-frequency).

I think this is probably too difficult to explain in the article, but if someone wants to take a crack at being bold and explaining it, please be my guest!

Atlant 12:18, 10 August 2006 (UTC)

 * There's a lot of confusion about this:       — Omegatron 14:54, 10 August 2006 (UTC)

(that is, the multiple sine waves that constitute) the antinoise signal are most definitely phase-reversed from their analagous components in the noise signal

 * But you didn't go in and phase-shift each individual frequency component; you flipped the whole signal over.

 * Such a phase shift in a real-life system would require a delay. — Omegatron 19:31, 25 August 2006 (UTC)

 * No, not for pure sine waves where a polarity reversal and a 180° phase shift are functionally identical: no delay required.

 * Atlant 18:11, 27 August 2006 (UTC)

 * Functionally identical, but not identical. In a real-life system, a phase shift requires a delay.  A phase shift of 35° and a phase shift of 180° are more closely related than a polarity flip. — Omegatron 19:24, 27 August 2006 (UTC)

 * I'm sorry, but you're wrong. For a sine wave, the results are indistinguishable.

 * Atlant 02:22, 28 August 2006 (UTC)

 * That's what I just said. The results are indistinguishable, but the methods used are not. — Omegatron 03:04, 28 August 2006 (UTC)

Active Noise Controller
I would like to know about the companies who can supply active noise cancellation ear defenders and also DSP based active noise controller (with adaptive algorithm or LMS- & FXLMS algorithm.

Thanks for your valuable reply.

 * Google would be the obvious place to start.

 * By the way, you can "sign" your talk postings by including four tildes ( ~ ) after your post. When you press "Save page", these will be converted into your username or IP address in a handy, Wikilinked format. A timestamp for your post will also be included.

 * Atlant 14:03, 17 February 2006 (UTC)

A removed description
I've removed this recently-added text from the article. To me, the description farther up in this talk page is more accurate. This newer description doesn't include the simple nearly-instantaneous, band-limited feedback mechanism that is commonly used in ANC headphones.

 * Several different types of noise cancellation are possible. First is feedback, where a periodic signal is processed to produce a periodic signal of the opposite phase at a certain location of space, usually near an error microphone. This requires the noise signal to be periodic. Secondly is the feedfoward system, in which noise is recorded along a path between the noise and cancellation actuator(s). In a causal system, noise is recorded close to the source such that sound of an opposite phase can intercept it along a path. This system does not require the signal to be periodic.

 * Atlant 21:35, 20 March 2006 (UTC)

 * Unfortunately this description is much better than the one in the article. It has the virtue of being more complete. The article concentrates overmuch on FFT based, periodic, type cancellation. Real world cancellation of impact type noise has been demonstrated, and the sstem I used was based on time history filtering, not FFTs. Greglocock 10:18, 22 February 2007 (UTC)

Applications
Shouldn't this page talk about, well, applications? Like military firing ranges, high-noise industrial areas? The first part actually seems to be talking about Types. Bihal 05:45, 28 April 2006 (UTC)

 * Yes. Please be bold and add to the article!

 * Atlant 13:13, 28 April 2006 (UTC)

Phase Cancellation of Visible Light Rays [?]
I'm curious as to whether it is (at least theoreticaly) possible to cancel the light rays of the visible spectrum through polarity reversal and/or 180° phase shift.

Could it be possible to generate a frequency that effectively cancels the phases of the ROYGBIV light rays?

And if so, then... 1.) would this create a state of total darkness?, or rather some other visible sensation? And... 2.) could such a high frequency possibly be generated with extant radio and multimedia hardware?

[It's a big question, but also one that has been nagging at me for quite some time :P ] Pine 16:20, 18 July 2007 (UTC)

Check out wave particle duality, and coherence, and interferometry. Roughly speaking, yes it is sort of possible, but only for 'short' distances. Greglocock 03:45, 21 July 2007 (UTC)

 * with the current technology it would be possible to accuratly control the phase of a very short laser puls (femtoseconds long) at a chosen frequency using high-resolution spectral phase shapers. Using two of these setups in a controlled environement would cause cancelation of the lightpuls. But to cancel a short controlled puls is something entirely different than to cancel a diffuse lightsource with a wide spectrum. Creating the right frequencies could be done using liquid cristals (LCD screens), but since the area in which a random lightsource would be coherent with the generated cancelation source is only several nanometers at max, the cancelation area would also be several nanometers, shorter than the wavelenght of light (800nm) and therefor does only alter the light, not cancel it. (i'm no optical scientist; imperfection at complete certainty) Frodo Muijzer (talk) 10:37, 23 October 2008 (UTC)

Polarity v. phase again
I can't see any support for the idea that sound waves have "polarity" at all—rather (mainly)) electrical signals do (as do light waves). It appears that one (but not the only) way to generate a phase-reversed wave is to invert the polarity of a signal simultaneously. Are there any references to the polarity of sound waves in the first place? Bongo  matic  05:36, 3 December 2009 (UTC) hello i live nest to people that will not shut up .. i wanted to makes my computer shut them up. can i do this some how.. come on people it's 2011  —Preceding unsigned comment added by 74.215.3.182 (talk) 21:04, 6 March 2011 (UTC)

I agree that sound waves do not have the kind of polarization (waves) that light waves have.

I hope you agree with me that rapid changes in air pressure -- above and below some average air pressure -- are perceived as sounds. Also, I hope you agree with me that if the air pressure at the ear is maintained at some extremely slowly changing or constant pressure, no sound can be heard.

When a speaker pushes out on the air in front of it, that causes the air to compress to a slightly higher-than-average air pressure. When a speaker pulls in, that causes rarefaction in the air to a slightly lower-than-average air pressure.

In this article, by "invert the polarity", we mean that (a) when some noise source causes rarefaction, the anti-noise speaker pushes out, also (b) when some noise source causes compression, the anti-noise speaker pulls in. In both cases, maintaining the air -- at the ear -- at very close to the average air pressure, so very little sound can be heard.

Is there some way other than "invert the polarity" that would be just as easy to understand and avoid the incorrect implication that sound waves have polarization (waves)?

How can we improve this article to make it easier to understand? --DavidCary (talk) 13:47, 16 March 2013 (UTC)

Theory and References
I plan on adding more theory on the physics behind Active Noise Control. Additionally I think providing more information from reliable white paper research will enhance the article. Bartscrc-NJITWILL (talk) 01:45, 10 November 2011 (UTC)

Trumpets
Dumb post - Has this been used/tried for trumpets. Even the best trumpet practice mutes don't sound that good/real ( at least to me ) and the back pressure is distressing ( at least to me ). If a device could be attached... to a trumpet bell could it kill the sound in the room while I blasted away and got a more real but reduced sound in a headphone. 24.128.186.53 (talk) 00:19, 12 February 2015 (UTC)

 * I'd say it is possible to reduce the average sound level, but I doubt you'd easily quieten the initial attack phase. Not a dumb question at all actually. Greglocock (talk) 02:22, 12 February 2015 (UTC)

Another dumb question ( seeing as how this site seems to have engineers/phd;s/? on it ) - is it the difference notes, the rapid chance in notes and/or the range of notes that make this hard to do. If it was easy I suspect some manufacturer - Yamaha/Bach/etc would have done tis long ago. Why does the "initial attack phase matter"? Another dumb question - why is the "initial attack phase" different and/or a problem. Thanks 2601:181:8301:4510:A1F7:777A:2085:58A (talk) 15:03, 30 April 2018 (UTC)

 * Initial attack phase? Someone ought to tell Chris Goldscheider. But I guess it's a bit late now. Martinevans123 (talk) 15:59, 30 April 2018 (UTC)

Eurovision anti-booing technology
I have seen no evidence at all that this uses ANC, which would be tricky in any case. The only technical description suggests they are using masking, ie drowning out the boos with applause. Greglocock (talk) 03:21, 12 July 2015 (UTC)

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Are there any working sound cancelling machines that I can buy?
Non ear phones, for places like apartments etc? What is the reason there are mostly only Sound Canceling Ear Phones? — Preceding unsigned comment added by 0wl (talk • contribs) 18:20, 10 February 2017 (UTC)
 * Active noise cancellation can only be applied to headphones because the noise profile that needs to be cancelled differs significantly from location to location (even across the small space of an apartment). A noise signal that might cancel out ambient noise at your couch might significantly add to that same noise in your kitchen, etc. WikiDan61 ChatMe!ReadMe!! 18:49, 10 February 2017 (UTC)

Fantastic reply, Dan, thank you! — Preceding unsigned comment added by 0wl (talk • contribs) 19:01, 10 February 2017 (UTC)

 * I'm glad you think its fantastic but it is wrong. Noise cancellation in large volumes is practical, and does not necessarily increase the noise anywhere outside of the cancellation area. For instance, many years ago somebody built an exhaust noise canceller for a ship. That seems to have worked quite well. I installed a noise cancellation system on a car's outside to reduce the exhaust noise. It was successful but impractical. In resonant cavities such as inside a car the cancellation system does not work the way you think it might, effectively it couples the acoustic resonances to the electronics, and the sound energy is turned into heat.  However there is no effective general purpose ANC system that I know of. I could probably knock one together for a specific environment, but it would not be cheap. Also there are some noises that would be very hard to cancel. The reason it works well with engines and things like that is that you know exactly what the frequency is that you need to kill. It is possible to cancel non deterministic noise in some cases, but not in general. Greglocock (talk) 23:46, 10 February 2017 (UTC)
 * ... "exhaust noise canceller for a ship." Martinevans123 (talk) 23:50, 10 February 2017 (UTC)

 * Sorry, I haven't worked in that field for 27 years, I can't remember who did it (Lord I suspect) or the timeframe, 60s probably. Here's a neat summary of ANC, including a discussion of free field cancellation and a refutation of the statement about noisier elsewhere - http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.569.5748&rep=rep1&type=pdf  and here's a more modern ship based system http://www.jime.jp/e/publication/bulletin/english/pdf/mv29n012001p35.pdf  . Incidentally the first ANC demo by Lotus used a very simple setup that was manually tuned on the fly, basically fiddling with the phase and amplitude of the speaker by fiddling with two knobs. Greglocock (talk)

 * Actually, both statements are somewhat correct. There are basically two different approaches to cancelling noise: 1) cancelling noise locally at a specific point via a control source that is placed away from the noise source or 2) cancelling noise globally with control sources which are very close to the noise source. The second approach uses the fact that the total sound power output can be minimized, if the noise source and the control source are closer than half a wavelength apart. That means for the first approach, that the total sound power is always increased if the distance is larger than half a wavelength (see e.g. section 8.4. in Nelson and Elliott, "Active Control of Sound", Academic Press, 1992). Fhchl (talk) 15:16, 16 September 2021 (UTC)

Hyundai RANC
I realise without refs this cannot go into the main article, but the first time I saw an accelerometer based feedforward ANC to cancel road noise was in the late 80s at Lotus. It was fitted to a large Audi and a Porsche. I don't know if either company took it to production. Hence Hyundai's claim of a 'first' is rather inaccurate. Greglocock (talk) 07:29, 20 February 2020 (UTC)

Adaptive noise cancellation
Need your thoughts on whether this should be a separate topic from Noise cancellation or Adaptive filtering. It appears to be someone's research material. Please help discuss at Draft:Adaptive noise cancelling. AngusW🐶🐶F ( bark  •  sniff ) 18:52, 21 January 2023 (UTC)

title: Talk:Active noise control


text: User talk:84.56.145.156

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: User talk:84.56.145.156


text:
Carl Valentine

Carl Howard Valentine (born 4 July 1958) is a former professional soccer player and coach who has had a long association with soccer in the Vancouver area.

Born in England, he played for the Canada national team at international level.

He was the head coach of Ottawa Fury in the USL Premier Development League until taking the position as Vancouver Whitecaps FC club ambassador and staff coach in 2010, in the lead-up to the Whitecaps inaugural season in Major League Soccer.

Club career
Valentine had a career from the late 1970s to the late 1990s with several clubs, notably the Vancouver Whitecaps of the North American Soccer League, Oldham Athletic, West Bromwich Albion of the Football League, and the Vancouver 86ers of the Canadian Soccer League and later American Professional Soccer League.

A striker, Valentine began his pro career in 1976 as a 17-year-old with Football League Second Division side Oldham Athletic. Valentine signed with the Vancouver Whitecaps and as a rookie helped them win their only North American Soccer League championship in 1979. Liking life in Vancouver, Valentine became a Canadian citizen in 1983. The lure of top division English soccer saw Valentine sign with West Midlands side West Brom in 1984. Until 2011, Valentine was the last player to have scored a winning goal for Albion against their local rivals Aston Villa, having scored the only goal of the game in a 1–0 win in 1985. After two seasons with the Baggies, in which he played 44 first-team games and scored 6 times, Valentine returned to Vancouver to play for the new franchise Vancouver 86ers, where he remained for the next 13 years. Retiring as a full-time player in 1992, Valentine was player/manager of the club until retiring in 1999.

On 22 November 1985, Valentine signed with the Cleveland Force of the Major Indoor Soccer League. Valentine played three seasons with the Force which folded during the 1988 off season. He then signed with the Baltimore Blast. In June 1990, Valentine signed a one-year contract with the Blast only to be traded to the Kansas City Comets in exchange for Dale Mitchell on 21 August 1990. The Comets folded at the end of the season and in September 1991, Valentine signed with the Tacoma Stars.

International career
Initially hoping to be selected to play for England at some point, Valentine passed on an offer to play for Canada at the 1984 Summer Olympics. He decided in 1985 however to declare his allegiance to his new home country and made his debut for Canada in a September 1985 FIFA World Cup qualification match against Honduras. Despite a bad case of influenza, Valentine famously assisted on both goals (with corner kicks) Canada scored to defeat Honduras 2–1 to advance to the World Cup Finals for the first time.

He earned a total of 31 caps, scoring 1 goal. He represented Canada in 9 World Cup qualifiers and played in all three of the country's first-round games in the 1986 World Cup. His final international was a 15 August 1993 World Cup qualification match against Australia in Sydney, a game which also marked the end of the international careers of Dale Mitchell and Mike Sweeney.

Personal life
Valentine has two daughters, Keelie and Shannon, and a son, Gavin. He is currently a Residency coach and Club Ambassador for Whitecaps FC. Valentine is partly of Jamaican descent.

Career statistics

 * Scores and results list Canada's goal tally first.

title: Carl Valentine


text:
Trends (journals)

Trends is a series of 16 review journals in a range of areas of biology and chemistry published under its Cell Press imprint by Elsevier. The publisher in lieu is Danielle Loughlin.

The Trends series was established in 1976 with Trends in Biochemical Sciences, rapidly followed by Trends in Neurosciences, Trends in Pharmacological Sciences, and Immunology Today.

Immunology Today, Parasitology Today, and Molecular Medicine Today changed their names to Trends in... in 2001. Drug Discovery Today was spun off as an independent brand.

Titles
The current set of Trends journals are all published monthly:

title: Trends (journals)


text:
Damping

In physical systems, damping is the loss of energy of an oscillating system by dissipation. Damping is an influence within or upon an oscillatory system that has the effect of reducing or preventing its oscillation. Examples of damping include viscous damping in a fluid (see viscous drag), surface friction, radiation, resistance in electronic oscillators, and absorption and scattering of light in optical oscillators. Damping not based on energy loss can be important in other oscillating systems such as those that occur in biological systems and bikes (ex. Suspension (mechanics)). Damping is not to be confused with friction, which is a type of dissipative force acting on a system. Friction can cause or be a factor of damping.

The damping ratio is a dimensionless measure describing how oscillations in a system decay after a disturbance. Many systems exhibit oscillatory behavior when they are disturbed from their position of static equilibrium. A mass suspended from a spring, for example, might, if pulled and released, bounce up and down. On each bounce, the system tends to return to its equilibrium position, but overshoots it. Sometimes losses (e.g. frictional) damp the system and can cause the oscillations to gradually decay in amplitude towards zero or attenuate. The damping ratio is a measure describing how rapidly the oscillations decay from one bounce to the next.

The damping ratio is a system parameter, denoted by $ζ$ ("zeta"), that can vary from undamped ($ζ = 0$), underdamped ($ζ < 1$) through critically damped ($ζ = 1$) to overdamped ($ζ > 1$).

The behaviour of oscillating systems is often of interest in a diverse range of disciplines that include control engineering, chemical engineering, mechanical engineering, structural engineering, and electrical engineering. The physical quantity that is oscillating varies greatly, and could be the swaying of a tall building in the wind, or the speed of an electric motor, but a normalised, or non-dimensionalised approach can be convenient in describing common aspects of behavior.

Oscillation cases
Depending on the amount of damping present, a system exhibits different oscillatory behaviors and speeds.
 * Where the spring–mass system is completely lossless, the mass would oscillate indefinitely, with each bounce of equal height to the last. This hypothetical case is called undamped.
 * If the system contained high losses, for example if the spring–mass experiment were conducted in a viscous fluid, the mass could slowly return to its rest position without ever overshooting. This case is called overdamped.
 * Commonly, the mass tends to overshoot its starting position, and then return, overshooting again. With each overshoot, some energy in the system is dissipated, and the oscillations die towards zero. This case is called underdamped.
 * Between the overdamped and underdamped cases, there exists a certain level of damping at which the system will just fail to overshoot and will not make a single oscillation. This case is called critical damping. The key difference between critical damping and overdamping is that, in critical damping, the system returns to equilibrium in the minimum amount of time.

Damped sine wave

A damped sine wave or damped sinusoid is a sinusoidal function whose amplitude approaches zero as time increases. It corresponds to the underdamped case of damped second-order systems, or underdamped second-order differential equations. Damped sine waves are commonly seen in science and engineering, wherever a harmonic oscillator is losing energy faster than it is being supplied. A true sine wave starting at time = 0 begins at the origin (amplitude = 0). A cosine wave begins at its maximum value due to its phase difference from the sine wave. A given sinusoidal waveform may be of intermediate phase, having both sine and cosine components. The term "damped sine wave" describes all such damped waveforms, whatever their initial phase.

The most common form of damping, which is usually assumed, is the form found in linear systems. This form is exponential damping, in which the outer envelope of the successive peaks is an exponential decay curve. That is, when you connect the maximum point of each successive curve, the result resembles an exponential decay function. The general equation for an exponentially damped sinusoid may be represented as: $$y(t) = A e^{-\lambda t} \cos(\omega t - \varphi)$$ where:
 * $$y(t)$$ is the instantaneous amplitude at time $t$;
 * $$A$$ is the initial amplitude of the envelope;
 * $$\lambda$$ is the decay rate, in the reciprocal of the time units of the independent variable $t$;
 * $$\varphi$$ is the phase angle at $t = 0$;
 * $$\omega$$ is the angular frequency.

Other important parameters include:
 * Frequency: $$f = \omega / (2\pi)$$, the number of cycles per time unit. It is expressed in inverse time units $$t^{-1}$$, or hertz.
 * Time constant: $$\tau = 1 / \lambda$$, the time for the amplitude to decrease by the factor of e.
 * Half-life is the time it takes for the exponential amplitude envelope to decrease by a factor of 2. It is equal to $$\ln(2) / \lambda$$ which is approximately $$0.693 / \lambda$$.
 * Damping ratio: $$\zeta$$ is a non-dimensional characterization of the decay rate relative to the frequency, approximately $$\zeta = \lambda / \omega$$, or exactly $$\zeta = \lambda / \sqrt{\lambda^2 + \omega^2} < 1$$.
 * Q factor: $$Q = 1 / (2 \zeta)$$ is another non-dimensional characterization of the amount of damping; high Q indicates slow damping relative to the oscillation.

Damping ratio definition

The damping ratio is a parameter, usually denoted by ζ (Greek letter zeta), that characterizes the frequency response of a second-order ordinary differential equation. It is particularly important in the study of control theory. It is also important in the harmonic oscillator. In general, systems with higher damping ratios (one or greater) will demonstrate more of a damping effect. Underdamped systems have a value of less than one. Critically damped systems have a damping ratio of exactly 1, or at least very close to it.

The damping ratio provides a mathematical means of expressing the level of damping in a system relative to critical damping. For a damped harmonic oscillator with mass m, damping coefficient c, and spring constant k, it can be defined as the ratio of the damping coefficient in the system's differential equation to the critical damping coefficient:

 * $$ \zeta = \frac{c}{c_c} = \frac {\text{actual damping}} {\text{critical damping}},$$

where the system's equation of motion is
 * $$ m\frac{d^2x}{dt^2} + c\frac{dx}{dt} + kx = 0 $$.

and the corresponding critical damping coefficient is
 * $$ c_c = 2 \sqrt{k m} $$

or
 * $$ c_c = 2 m \sqrt{\frac{k}{m}} = 2m \omega_n $$

where
 * $$ \omega_n = \sqrt{\frac{k}{m}} $$ is the natural frequency of the system.

The damping ratio is dimensionless, being the ratio of two coefficients of identical units.

Derivation
Using the natural frequency of a harmonic oscillator $\omega_n = \sqrt{{k}/{m}}$ and the definition of the damping ratio above, we can rewrite this as:
 * $$ \frac{d^2x}{dt^2} + 2\zeta\omega_n\frac{dx}{dt} + \omega_n^2 x = 0. $$

This equation is more general than just the mass–spring system, and also applies to electrical circuits and to other domains. It can be solved with the approach
 * $$ x(t) = C e^{s t},$$

where C and s are both complex constants, with s satisfying
 * $$ s = -\omega_n \left(\zeta \pm i \sqrt{1 - \zeta^2}\right). $$

Two such solutions, for the two values of s satisfying the equation, can be combined to make the general real solutions, with oscillatory and decaying properties in several regimes:
 * Undamped: Is the case where $$\zeta = 0$$ corresponds to the undamped simple harmonic oscillator, and in that case the solution looks like $$\exp(i\omega_nt)$$, as expected. This case is extremely rare in the natural world with the closest examples being cases where friction was purposefully reduced to minimal values.
 * Underdamped: If s is a pair of complex values, then each complex solution term is a decaying exponential combined with an oscillatory portion that looks like $\exp\left(i \omega_n \sqrt{1 - \zeta^2}t\right)$ . This case occurs for $$ \ 0 \le \zeta < 1 $$, and is referred to as underdamped (e.g., bungee cable).
 * Overdamped: If s is a pair of real values, then the solution is simply a sum of two decaying exponentials with no oscillation. This case occurs for $$ \zeta > 1 $$, and is referred to as overdamped. Situations where overdamping is practical tend to have tragic outcomes if overshooting occurs, usually electrical rather than mechanical. For example, landing a plane in autopilot: if the system overshoots and releases landing gear too late, the outcome would be a disaster.
 * Critically damped: The case where $$ \zeta = 1 $$ is the border between the overdamped and underdamped cases, and is referred to as critically damped. This turns out to be a desirable outcome in many cases where engineering design of a damped oscillator is required (e.g., a door closing mechanism).

Q factor and decay rate
The Q factor, damping ratio ζ, and exponential decay rate α are related such that

\zeta = \frac{1}{2 Q} = { \alpha \over \omega_n }. $$

When a second-order system has $$\zeta < 1$$ (that is, when the system is underdamped), it has two complex conjugate poles that each have a real part of $$-\alpha$$; that is, the decay rate parameter $$\alpha$$ represents the rate of exponential decay of the oscillations. A lower damping ratio implies a lower decay rate, and so very underdamped systems oscillate for long times. For example, a high quality tuning fork, which has a very low damping ratio, has an oscillation that lasts a long time, decaying very slowly after being struck by a hammer.

Logarithmic decrement

For underdamped vibrations, the damping ratio is also related to the logarithmic decrement $$\delta$$. The damping ratio can be found for any two peaks, even if they are not adjacent. For adjacent peaks:
 * $$ \zeta = \frac{\delta}{\sqrt{\delta^2 + \left(2\pi\right)^2}}$$ where $$\delta = \ln\frac{x_0}{x_1}$$

where x0 and x1 are amplitudes of any two successive peaks.

As shown in the right figure:

 * $$ \delta = \ln\frac{x_1}{x_3}=\ln\frac{x_2}{x_4}=\ln\frac{x_1-x_2}{x_3-x_4}$$

where $$x_1$$, $$x_3$$ are amplitudes of two successive positive peaks and $$x_2$$, $$x_4$$ are amplitudes of two successive negative peaks.

Percentage overshoot
In control theory, overshoot refers to an output exceeding its final, steady-state value. For a step input, the percentage overshoot (PO) is the maximum value minus the step value divided by the step value. In the case of the unit step, the overshoot is just the maximum value of the step response minus one.

The percentage overshoot (PO) is related to damping ratio (ζ) by:

 * $$ \mathrm{PO} = 100 \exp \left({-\frac{\zeta\pi}{\sqrt{1-\zeta^2}}}\right) $$

Conversely, the damping ratio (ζ) that yields a given percentage overshoot is given by:

 * $$ \zeta = \frac{-\ln\left(\frac{\rm PO}{100}\right)}{\sqrt{\pi^2 + \ln^2\left(\frac{\rm PO}{100}\right)}} $$

Viscous drag
When an object is falling through the air, the only force opposing its freefall is air resistance. An object falling through water or oil would slow down at a greater rate, until eventually reaching a steady-state velocity as the drag force comes into equilibrium with the force from gravity. This is the concept of viscous drag, which for example is applied in automatic doors or anti-slam doors.

Damping in electrical systems
Electrical systems that operate with alternating current (AC) use resistors to damp the electric current, since they are periodic. Dimmer switches or volume knobs are examples of damping in an electrical system.

Magnetic damping and Magnetorheological damping
Kinetic energy that causes oscillations is dissipated as heat by electric eddy currents which are induced by passing through a magnet's poles, either by a coil or aluminum plate. Eddy currents are a key component of electromagnetic induction where they set up a magnetic flux directly opposing the oscillating movement, creating a resistive force. In other words, the resistance caused by magnetic forces slows a system down. An example of this concept being applied is the brakes on roller coasters.

Magnetorheological Dampers (MR Dampers) use Magnetorheological fluid, which changes viscosity when subjected to a magnetic field. In this case, Magnetorheological damping may be considered an interdisciplinary form of damping with both viscous and magnetic damping mechanisms.

title: Damping


text:
Grand Victoria Casino Elgin

The Grand Victoria Casino Elgin is a riverboat casino in Elgin, Illinois, United States, located about 40 mi west of Chicago. It is owned and operated by Caesars Entertainment.

History
The casino was developed by Gold Strike Resorts and Hyatt. It opened its doors on October 6, 1994.

Gold Strike was acquired in 1995 by Circus Circus Enterprises, which later changed its name to Mandalay Resort Group, and was then acquired by MGM Mirage in 2005. At the time of the merger in 2005, management of the property was transferred from Mandalay to Hyatt.

In August 2018, MGM and Hyatt sold the casino to Eldorado Resorts (later renamed as Caesars Entertainment) for $328M.

Casino
The casino employs about 1,440 people. The 29850 sqft facility consists of approximately 1,100 video poker and slot machines in addition to 36 table games.

In addition to games, the casino has banquet and dining facilities including Buckinghams, Crave Deli, and Slice Pizzeria.

Economic contributions
Each year the Grand Victoria Casino Elgin donates 7.5% of its adjusted net operating income to the Kane County Board and 12.5% to the Grand Victoria Foundation. In 2008, Kane County received about $8 million to use for internal programs, about $1 million of which was available for projects benefiting the county's educational, environmental, and economic needs. Grants for these projects are recommended by Kane County's riverboat committee, but both the executive committee and the county board must approve the funds before they can be distributed.

In addition to the Kane County Board and the Grand Victoria Foundation, The city of Elgin receives its own portion of the Grand Victoria's revenue. Casino profits led to the removal of the $25 vehicle license fee as well as a yearly property tax rebate for senior citizens. Today, the city continues to allocate funds for housing restoration. In 2007 specifically, the city allocated twice as much money as usual for housing rehabilitation. Money is also dedicated to the following causes:
 * Toy collecting
 * Not-for-profit organizations

The Grand Victoria Foundation sponsors additional community programs, such as film screenings, at Gail Borden Public Library in Elgin.

Revenue reports since 2000
According to the Daily Herald, in 2007 the Grand Victoria Casino Elgin generated more revenue than any other Illinois casino,taking in $437 million, a rise of 13% since 2000. This increase in revenue came as a result of tightening slot machines, and occurred despite a 32% drop in attendance between 2000 and 2007.

As Illinois Gaming Board reports illustrate, the 2008-2009 economic recession led to an overall decrease in revenue among Illinois casinos, particularly the Grand Victoria. The casino's revenue of $25 million for the month of February, 2009 was down 9.9% from the previous year and down 24% from 2007. The Smoke Free Illinois Act, which banned smoking in all enclosed workplaces beginning January 1, 2008, also severely reduced casino attendance. Casino industry officials estimated that Illinois would receive about 20% less in monetary contributions from the casino over the course of 2008, a difference of nearly $144 million.

In an attempt to make up for lost revenue, the Grand Victoria and other Illinois riverboat casinos petitioned for permission to distribute free alcoholic beverages. Supporters of a proposed bill said that the existing law was unclear, while opposing groups cited increased gambling addiction as a likely consequence if free alcohol distribution were to be legalized.

In 2018, the Grand Victoria was third among Illinois riverboat casinos, with gross receipts of $160.7 billion.

title: Grand Victoria Casino Elgin


text:
Talk:Tony Benn

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External links modified
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War service
The Atomic bombings of Hiroshima and Nagasaki took place on 6th and 9th of August 1945, and the Japanese Emperor announced Japans surrender to the Allies on August 15.

Currently the article states:

The last clause in this sentence is misleading because, particularly the phrase "just days before", it imples that Benn was privy to the events of August 1945 prior to their happening, and so knew that the war was effectivly over. It is unlikely that he was. I have no idea why he resigned his commission or even why it was accepted, but it was not because he or his immediate superiors in early August 1945 could know that the war would be over by the middle of the month.

I suggest that either the last clause is removed or that it is altered to explain his motive (eg "because he thought it unlikely that he would serve in the war against Japan and he wished to ...").

-- PBS (talk) 11:06, 29 January 2019 (UTC)

Mao
My edit of the Tony Benn page keeps getting reversed. An entry from Benn's diary is not relevant to his record as member of the government. A whole paragraph on his views on Mao Zedong are digressive, when a brief sketch of his actions as government minister are being discussed. The source in question is a newspaper column written by a journalist who is frank in admitting his hostility to Benn. The inclusion of the quote, presented at such length, suggests a strong political bias. — Preceding unsigned comment added by Benjamin 096 (talk • contribs) 17:34, 29 August 2020 (UTC)
 * There are other reliable sources that support Benn's attitude to Mao. Graham Beards (talk) 17:42, 29 August 2020 (UTC)

I'm not disputing the truth of the statement so much as its relevance. Why is an entire paragraph devoted to his views on Mao? There are more words devoted to this than to his work as a government minister. The subject heading is "In government, 1974–1979", and as such, should be devoted to his actions as a member of the government. If it is felt that this opinion should be included, surely not at such length, and in this part of the page? If it is to be included at all I would suggest truncating it to a more suitable length, and removing it to another part of the page. — Preceding unsigned comment added by Benjamin 096 (talk • contribs) 17:51, 29 August 2020 (UTC)

 * I think there is some truth in Benjamin 096's comment, as it does not relate directly to Benn's role in the Wilson/Callaghan government of 1974-79. It does, however, illustrate a certain amount of naive optimism about Mao's government. It might fit in better somewhere else in the article, but there isn't a "Personal views" section.-- ♦Ian Ma c M♦  (talk to me) 19:35, 29 August 2020 (UTC)
 * Yes, I agree. Graham Beards (talk) 20:25, 29 August 2020 (UTC)

1967 photo versus 2006 photo
I propose changing the lead (infobox) photograph to one from Benn's ministerial career. I edited to Tony Benn 1967.jpg (below) and moved the current 2006 photo to the "later life" section. User:Helper201 reverted pending a consensus; fair enough—I outline my reasoning below.

I have been unable to find firm standing authority to cite, but my solid understanding is that for living persons, it is best practice to use recent photographs, while for persons who have passed on, it is best practice to use a photograph which represents the individual at (for lack of better phrasing) their peak notoriety. While Benn had a long career and was notable essentially the whole way through, it seems best practice here to use a photograph from his time in cabinet. The current 2006 photo is from his post-Westminster days, when he remained very much a public figure but not so much a powerful politician; my proposed replacement is from his time in the Second Wilson cabinet. Ideally, we would have a picture from 1974–75, when he was both Secretary of State for Industry and a contender for Prime Minister, but no such photograph is available on the Commons, so I went with this option for now. -A-M-B-1996- (talk) 17:25, 6 August 2023 (UTC)

 * Oppose. The newer image is of vastly superior quality. ‑‑Neveselbert (talk · contribs · email) 00:11, 7 August 2023 (UTC)
 * Oppose. I agree with the above that the 2006 image is of much better quality and should be retained in the infobox. Helper201 (talk) 13:34, 7 August 2023 (UTC)

title: Talk:Tony Benn


text:
Talk:Edwin Markham

Comments
The forgotten work of Edwin Markham has to be his 'The Real America in Romance', a history of the United States from 1435 to the first decade of the 20th century. It was published by Funk and Wagnells in 1910 just before the First World War and comprises approx. 15 volumes illustrated. In it Markham takes fictional caricatures of peoples at each time frame and has them interact with real historical(caricatures) characters in fictional settings. For it being a romantic literary work it comes disturbingly close to the main stream tellings of U.S. history in the text books used by public schools. This is probably why you can come across it at any decent sized Catholic bookshop. One store said something like this about it, 'Profusely illustrated with portraits of historical characters and views of the sacred places of our native land.'

Any idea when The Right Kind of People was published?
I would like to add the poem "The Right Kind of People" to wikisource, if it is out of copyright. However, I don't know when it was published. It was published in "The Best Loved Poems of the American People" in 1936, but in that case it might still be in copyright. Any idea when and where it was first published? Thanks. Jrincayc 04:03, 25 May 2007 (UTC)

Historical Landmark
The California Historical Landmarks in Santa Clara County points to this article for the landmark:  Edwin Markham House. Please use the Template:Infobox historic site to update the article with the following citation #1 and citation #2. Greg Henderson (talk) 21:59, 26 September 2023 (UTC)
 * That template is for articles about historical sites. This is an article about a person, it does not belong here. Melcous (talk) 11:55, 27 September 2023 (UTC)

title: Talk:Edwin Markham


text:
Saint David Parish, Grenada

Saint David's Parish is the fourth largest of the parishes of Grenada in the island's southeast. The parish's main town (largest village) is St. David's, located between La Tante and Westerhall. Because St David's is so small, the parish is sometimes referred to as "The Virgin Parish".

The parish's coast to its east has spectacular headlands, bays and inlets. The unspoilt rocky coastline slopes up gently towards the central mountainous ridge. It is known for its undeveloped bucolic state and secluded beaches.

History
The town of Megrin was established at St David's Point in 1609 and destroyed during the 1795–96 Fedon conflict and the town never rebuilt. In the 1721 the Catholic parish of Megrin was reopened by the French, but it was built down next to the sea. In 1747 Megrin in St David was one of the six churches and parishes in Grenada. In 1795 the Fedon Rebellion became a battle between Fedon and the English troops staying at the church over night. In Grenada lies the area of Perdmontempts which is a mountainous area which includes many valleys bearing rich fruit such as guava, cherries, plums, mangoes and sugar cane.

The parish was also the home to the New Jewel Movement, which culminated in the Grenada Revolution on 13 March 1979. Its founders, Theodore Victor, aka "Teddy", Sebastian Thomas, Unison Whiteman, and Wally Jeremiah, all discontented with the opposition party Grenada National Party (GNP) under Herbert Blaize decided to build a grass roots movement that would organize and educate the Grenadian masses, publishing a weekly newspaper, The New Jewel.

St David's become the hotbed of political activity in the late 1970s culminating in a confrontation with the Gairy Regime over access to a popular beach LaSagess which had been bought by a British peer, Lord Brownlow, denying natives access to the popular beach. St David's had served the same purpose for Eric Gairy some twenty years earlier when he returned from Aruba to stake his political future. Being funded by rich natives in the St. David's parish Gairy burned plantations and estates in what came to be known as "Sky Red" in a rebellion against British Rule, eventually leading to Grenada's independence in 1974.

title: Saint David Parish, Grenada


text: Talk:Glittering generality

title: Talk:Glittering generality


text:
Bernard Prince

Bernard Prince is a Franco-Belgian comics series, featuring an eponymous character and his sailor-adventurer companions. The series was created by Belgian cartoonists Greg and Hermann for the Franco-Belgian comics magazine Tintin, first appearing on January 4, 1966.

Synopsis
Originally an agent of Interpol the heroic Prince, joined by the roguish Barney Jordan and the clever orphan Djinn, becomes an adventurer sailing through the contemporary (1960s-70s) world on a sloop, the beautiful Cormoran.

title: Bernard Prince


text:
Maksutov telescope

The Maksutov (also called a "Mak") is a catadioptric telescope design that combines a spherical mirror with a weakly negative meniscus lens in a design that takes advantage of all the surfaces being nearly "spherically symmetrical". The negative lens is usually full diameter and placed at the entrance pupil of the telescope (commonly called a "corrector plate" or "meniscus corrector shell"). The design corrects the problems of off-axis aberrations such as coma found in reflecting telescopes while also correcting chromatic aberration. It was patented in 1941 by Soviet optician Dmitri Dmitrievich Maksutov. Maksutov based his design on the idea behind the Schmidt camera of using the spherical errors of a negative lens to correct the opposite errors in a spherical primary mirror. The design is most commonly seen in a Cassegrain variation, with an integrated secondary, that can use all-spherical elements, thereby simplifying fabrication. Maksutov telescopes have been sold on the amateur market since the 1950s.

Invention
Dmitri Maksutov may have been working with the idea of pairing a spherical primary mirror in conjunction with a negative meniscus lens as far back as 1936. His notes from that time on the function of Mangin mirrors, an early catadioptric spotlight reflector consisting of negative lens with silvering on the back side, include a sketch of a Mangin mirror with the mirror part and the negative lens separated into two elements. Maksutov seems to have picked up the idea again in 1941 as a variation on an earlier design that paired a spherical mirror with a negative lens, Bernhard Schmidt's 1931 "Schmidt camera". Maksutov claimed to have come up with the idea of replacing the complex Schmidt corrector plate with an all-spherical "meniscus corrector plate" while riding in a train of refugees from Leningrad. Maksutov is described as patenting his design in May, August, or October 1941 and building a "Maksutov–Gregorian"-style prototype in October 1941. Maksutov came up with the unique idea using an "achromatic corrector", a corrector made of a single type of glass with a weak negative meniscus shape that departed from the pure concentric spherical symmetrical shape to correct chromatic aberration.

Similar independent meniscus telescope designs were also patented in 1941: Albert Bouwers (his 1941 concentric meniscus telescope), K. Penning and Dennis Gabor (a catadioptric non-monocentric design). Wartime secrecy kept these inventors from knowing about each other's designs, leading to each being an independent invention.

Derivative designs
Maksutov's 1944 design was the first-published meniscus telescope design, and was published in the widely-read Journal of the Optical Society of America. This led to professional and amateur designers almost immediately experimenting with variations, including Newtonian, Cassegrain, and wide-field camera designs.

Maksutov–Cassegrains
There are many Maksutov designs that use a Cassegrain configuration, mounting a convex secondary mirror near the focus of the primary mirror. Most types use full-aperture correctors and are therefore not very large, since the corrector plate rapidly becomes prohibitively large, heavy and expensive as the aperture increases, with very long cool-down times to reach optimal optical performance. Most commercial manufacturers usually stop at 180 mm (7 in).

Gregory or "spot" Maksutov–Cassegrains
Maksutov's design notes from 1941 explored the possibility of a 'folded' Cassegrain-type construction with a secondary silvered "spot" on the convex side of the meniscus facing the primary mirror. He thought this would create a sealed and rugged optical system suitable for use in schools. This design appeared commercially in Lawrence Braymer's 1954 Questar telescope and in PerkinElmer designer John Gregory's competing patent for a Maksutov–Cassegrain. Commercial use of Gregory's design was explicitly reserved for Perkin–Elmer but was published as an amateur telescope design in a 1957 issue of Sky and Telescope in and  variations. Most Maksutovs manufactured today are this type of 'Cassegrain' design (called either a "Gregory–Maksutov" or "Spot-Maksutov") that use all-spherical surfaces and have, as secondary, a small aluminized spot on the inner face of the corrector. This has the advantage of simplifying construction. It also has the advantage of fixing the alignment of the secondary and eliminates the need for a 'spider' that would cause diffraction spikes. The disadvantage is that, if all spherical surfaces are used, such systems have to have focal ratios above to avoid aberrations. Also, a degree of freedom in correcting the optical system by changing the radius of curvature of the secondary is lost, since that radius is the same as that of the rear meniscus face. Gregory himself, in a second, faster design, resorted to aspherization of the front corrector surface (or the primary mirror) in order to reduce aberrations. This has led to other designs with aspheric or additional elements to further reduce off-axis aberration. This type of Maksutov-Cassegrain's high focal ratio and narrower field of view makes them more suitable for lunar and planetary imaging and any other type of observing where a narrow field high power view is a plus, such as resolving tightly packed globular clusters and double stars.

The most notable early amateur astronomical type was the Questar 3-1/2 Maksutov Cassegrain introduced in 1954, a small-run, expensive model still available on the consumer market. The mid-1970s saw the introduction of mass-produced models by some of the major commercial manufacturers. More recently, low-cost Russian and, lately, Chinese mass-production has pushed the prices down even further. Many manufacturers currently produce Maksutov–Cassegrains, such as Explore Scientific, Intes, Intes-Micro, LOMO, Orion Optics, Telescope Engineering Company (TEC), Vixen, the Meade Instruments's ETX line, and the Synta Taiwan produced Celestron, Sky-Watcher and Orion Telescopes lines. The spot Maksutov–Cassegrain design has been used extensively in military, industrial, and aerospace applications. Since all of the optical elements can be permanently fixed in alignment and the tube assembly can be environmentally sealed, the design is extremely rugged. That makes it ideal for tracking, remote viewing, and radar calibration / boresighting, where instruments are subjected to severe environments and high g-forces.

Rutten Maksutov–Cassegrains
The Rutten Maksutov–Cassegrain (also called a Rumak or Sigler Maksutov) has a separate secondary mirror mounted on the inner surface of the meniscus corrector, sometimes similar to the corrector/mirror holder configurations found in commercial Schmidt–Cassegrains. This provides an extra degree of freedom in correcting aberration by changing the curvature of the corrector and the secondary independently. Specifically it allows the designer to aspherize the secondary to provide a much wider flat field than traditional spot Maksutovs, with less off-axis coma. Mounting the secondary on the corrector also limits diffraction spikes. This version is named after the work of Dutch optical designer Harrie Rutten.

Sub-aperture corrector Maksutov–Cassegrains
Maksutov noted in his designs that instead of using a full-aperture corrector, a small sub-aperture corrector could be placed in the converging light cone of the primary mirror and achieve the same effect. In the 1980s Dave Shafer and Ralph W. Field came out with sub-aperture Cassegrain designs based on this idea. The design reduces the mass and "cool-down time" of a full-aperture corrector. It has the drawbacks of an open, unsealed tube and requires a spider assembly to hold the secondary mirror and corrector, which inevitably affects image quality through diffraction artifacts. Also since the light passes through the corrector twice, the number of surfaces involved is increased, making it difficult to achieve good aberration correction. Sub-aperture corrector Maksutovs are currently manufactured by Vixen telescopes, their VMC (Vixen Maksutov Cassegrain) models.

Maksutov–Newtonians
Maksutovs optics can be used in Newtonian configurations that have minimal aberration over a wide field of view, with one-fourth the coma of a similar standard Newtonian and one-half the coma of a Schmidt-Newtonian. Diffraction can also be minimized by using a high focal ratio with a proportionally small diagonal mirror mounted on the corrector, allowing this design to achieve contrast and image quality approaching that of unobstructed high-end refractors (although with some vignetting when used photographically). Like the Maksutov–Cassegrain, the overall diameter of the optical system is limited, due to the mass of the corrector plate. Synta Taiwan currently produces a 190 mm version under the Sky-Watcher brand as does Explore Scientific with a 152 mm version designed in collaboration with astronomer David Levy.

Maksutov cameras
The Maksutov system can be used in a (rare) type of prime-focus ultra-wide-field astronomical camera design similar to the Schmidt camera. Like the Schmidt camera, the Maksutov camera has a curved focal plane.

title: Maksutov telescope


text:
May 11 (Eastern Orthodox liturgics)

May 10 – Eastern Orthodox Church calendar – May 12

All fixed commemorations below celebrated on May 24 by Orthodox Churches on the Old Calendar.

For May 11th, Orthodox Churches on the Old Calendar commemorate the Saints listed on April 28.

Saints

 * Martyr Evellius, under Nero (66)
 * Martyrs Maximus, Bassus, and Fabius (284–305)
 * Hieromartyr Mocius (Mucius), presbyter of Amphipolis in Macedonia, beheaded in Byzantium (288)
 * Martyr Armodius
 * Martyr Acacius of Lower Moesia
 * Saints Cyril and Methodius, Equal-to-the-Apostles and Enlighteners of the Slavs (869, 885) (see also: July 17 )
 * Saints Clement of Ohrid (916), Sabbas (10th century), Angelarius (Angelyar) (ca. 886), Gorazd (896), and Naum of Preslav (910) — Disciples of Saints Cyril and Methodius and missionaries of the Slavs, Wonderworkers and Equal-to-the-Apostles
 * Saint Rostislav the Prince of Great Moravia, Confessor of the Faith (870)  (see also: October 29)

Pre-Schism Western saints

 * Hieromartyr Anthimus of Rome, and martyrs Sisinius the deacon with Diocletius and Florentius (disciples of St. Anthimus), (284–305)
 * Saint Principia of Rome, a holy virgin in Rome and disciple of St Marcella (420)
 * Saint Mammertus, Archbishop of Vienne (475)
 * Saint Possessor of Verdun, Bishop of Verdun, he and his flock were greatly troubled by the barbarian invasions of Franks, Vandals and Goths (c. 486)
 * Saint Tudy (Tudinus, Tegwin, Thetgo), a disciple of St Brioc in Brittany (5th century)
 * Saint Credan of Cornwall, hogherd.
 * Saint Gangulphus (760)
 * Saint Fremund of Dunstable, Anglo-Saxon hermit, killed by his kinsman Oswy with the help of Danish invaders who had also murdered King Edmund (866)
 * Saint Odo of Cluny, the second Abbot of Cluny (942)
 * Saint Mayeul (Majolus, Maieul), Abbot of Cluny (994)
 * Saint Odilo of Cluny (1049)

Post-Schism Orthodox saints

 * Martyrs Olympia, abbess of Mytilene, and nun Euphrosyne (1235)
 * Saint Sophronius of the Kiev Caves, recluse (13th century)
 * Saint Nicodemus of Pec, Archbishop of Serbia (1324)
 * Hieromartyr Joseph, first Metropolitan of Astrakhan (1672)
 * Blessed Christopher of Georgia (Christesias), monk at the Monastery of St. John the Baptist, at the David Gareja monastery complex, "The Thebaid of Georgia" (1771/1871)
 * New Martyr Dioscorus (Dioscorides) the New, of Smyrna
 * New Martyr Argyrus (Argyrus, Argyres) of Thessalonica (1806/1808)
 * Saint Theophylact, bishop of Stavropol and Ekaterinodar (1872)

New martyrs and confessors

 * New Hieromartyr Michael Belorossov, priest (1920)
 * New Hieromartyr Alexander (Petrovsky), Archbishop of Kharkov (1940)

Other commemorations

 * Commemoration of the Founding of Constantinople (330) as Capital of the Roman Empire
 * Consecration of the Saint Sophia Cathedral in Kiev (960).

title: May 11 (Eastern Orthodox liturgics)


text:
Selkirk

Selkirk may refer to:

People

 * Alexander Selkirk, Scottish castaway who formed the basis for the novel Robinson Crusoe by Daniel Defoe
 * Selkirk (surname), surname origin, and list of people with the surname
 * Earl of Selkirk, a title in the Peerage of Scotland
 * James Douglas-Hamilton, Baron Selkirk of Douglas, Scottish politician and Life Peer, briefly 11th Earl of Selkirk
 * Thomas Douglas, 5th Earl of Selkirk, Scottish philanthropist who sponsored immigrant settlements in Canada

Places

 * Selkirk Mountains, in British Columbia, Canada, the Idaho panhandle, and far eastern Washington State, United States

Canada

 * Selkirk, Manitoba
 * Selkirk (federal electoral district), a federal riding in Manitoba
 * Selkirk (provincial electoral district), in Manitoba
 * Selkirk, Ontario
 * Fort Selkirk, Yukon

Chile

 * Alejandro Selkirk Island, in the Juan Fernández Archipelago, Valparaíso Region, Chile

Scotland

 * Selkirk, Scottish Borders, Scotland
 * Selkirk (Parliament of Scotland constituency)
 * Selkirkshire, Scotland

United States

 * Selkirk, Kansas, an unincorporated community
 * Selkirk, Missouri, a ghost town
 * Selkirk, New York, an unincorporated hamlet in the town of Bethlehem

Animals

 * Selkirk (horse), (1988–2013), a North American-bred, thoroughbred racehorse
 * Selkirk Rex, a breed of cat which named from Selkirk Mountains

Education

 * Selkirk College, a community college in British Columbia
 * Selkirk Secondary School, a high school in Kimberley, British Columbia

Sports

 * Selkirk F.C., a football club
 * Selkirk RFC, a rugby club
 * Winnipeg Selkirks, a former ice hockey team from Winnipeg, Canada, see List of ice hockey teams in Manitoba

Transportation

 * Selkirk (sternwheeler 1895)
 * HMS Selkirk (J18)
 * Selkirk hurdle, a freight train route in New York
 * Selkirk locomotive, a type of steam locomotive

Other uses

 * Selkirk Communications, a defunct Canadian radio and television broadcasting company
 * Selkirk Grace commonly recited before a Burns supper
 * Selkirk transmitting station, near Selkirk, Scotland
 * The animated movie 7 Sea Pirates, also known as "Selkirk, el verdadero Robinson Crusoe"

title: Selkirk


text:
Template talk:COTWs

Comments
I'd like to remove all the country COT[X]s. They are all quite obviously dead. Spanish Translations I'm not sure about; Gaming COTW is living on a tricke charge. The only Collaborations that don't perpetually appear to be on the brink of death are AID and the original COTW. -Litefantastic 16:52, 15 Apr 2005 (UTC)

 * The Australian COTW has been changed to a Australian Collaboration of the Fortnight, and is alive and well. As for the other countries listed, while their pulse is fading, they are still active.--Cyberjunkie 02:15, 16 Apr 2005 (UTC)

I've added the others that were not on the COTWs back in because they haven't been declared inactive nor have they been active. So I'm sticking them on here to see if interest does develop. If it doesn't then they should be stuck with the inactive collaborations. Falphin 18:48, 23 Jun 2005 (UTC)
 * Also they haven't been on this list so it is tough to say if they could become active or not. Falphin 18:50, 23 Jun 2005 (UTC)

I'm going to re-org slightly, so that non-niche global scope colabs are at the top of the list. Since at the moment they get burried with the niche topics, and look less global. --Barberio 10:47, 21 April 2006 (UTC)

Topical outline
I'm going to change the order, so items are sorted by topic. Maurreen 04:07, 22 April 2006 (UTC)
 * This was a good idea, since people are more intrested in topic, than how it's schedualed. --Barberio 13:27, 22 April 2006 (UTC)
 * Thank you :) Maurreen 18:22, 23 April 2006 (UTC)
 * Is there any way we can possibly shortern the template? Otherwise it tends to be too long, covering text in the COTW pages (for example, see WP:USCOTW, where this template covers the nomination instructions). Thanks, AndyZ t 20:02, 24 April 2006 (UTC)

Shortened
Is that better? Maurreen 03:19, 25 April 2006 (UTC)
 * Would it be possible to have a show/hide link using the NavFrame and etc classes or would this disrupt too many collaboration pages? --Squilibob 14:46, 16 May 2006 (UTC)
 * It's a Wiki, try it. -- Omniplex 06:32, 31 May 2006 (UTC)

Layout questions
For a discussion about the edit link see the Tnavbar talk page. For issues like align=right (floating), colour scheme, width, and line breaks see the talk page, it's more or less the same problem for various "sidebar" templates. -- Omniplex 06:32, 31 May 2006 (UTC)

Current articles in collaboration
I think it would be good to have another option listing current articles in collaboration. Then people could easily see about related articles in COTWs. Maurreen 17:35, 28 July 2006 (UTC)

WP:100K
Would WP:100K be appropriate for this template? - David Gerard 19:55, 14 September 2006 (UTC)

Updating to reflect other collabs
Just changing the text a tad - a number of collaborations are biweekly / monthly / ongoing... changing a little of the text to reflect this... Lee∴V (talk  •  contribs)  09:06, 29 July 2010 (UTC)

Inclusion requirement for this template
WP:Collaborations describes a "collaboration" as: Please make sure that pages added here specifically deal with single article collaborations, e.g. a Collaboration of the Month (COTM). This template is not a Wikiproject listing.– Sir Lionel, EG(talk) 06:46, 26 August 2012 (UTC)

title: Template talk:COTWs