studiot

Right at the beginning of your link. 'transmission line' A La Bailey et al. Bose are very late at the gate.

Thirty years, ago, sixty years ago these were called labyrinths not waveguides.

Do you offer full time courses?

The 'waveguide' (advertiser's version, not a physicist's) only works at one frequency (or a very small range of frequencies)

Loudspeaker magnets are big and heavy and do not vibrate. Yes the cones will still be driven I asume you mean on axis cancellation (along the axis between the two speakers)? A good variation of this experiment is to first test along the axis and then try again with different speaker separations. Surely you can do this from a mono source? Note that depending upon the speaker mounting/enclosure there will also be a backward wave so you will never achieve perfect cancellation. Result for Experiment B will depend upon what you mean by back to back and the same comment about mounting/enclosures apply. One other comment about experimental technique. There will be a lot of reflections in an enclosed space. This is why speakers are tested in the open air or an anechoic chamber. Final comment. There are noise cancelling devices based on doing exactly this for quietening heavy machinery (eg generators). That is, a loudspeaker outputs an antiphase sound to that produced by the machine which cancels out the machine noise. They are very effective but rely on being set up exactly right for the machine and its housing.

Hear! Hear! +1

What I don't understand is why you don't respond directly to material I post, specifically designed to help you. For instance you responded to my post #39 by copying tables of standard integrals and derivatives. I have no idea what that achieved. I repeat my conviction that you need to connect mathematics to its applications to progress, particularly in numical methods for they are all about applications. So why don't you try the question in my post#39? A very good series of books at your level for your purposes is the Edward Arnold Modular Mathematics series. In particular the book by Berry and Houston " Mathematical Modelling" Is all about connecting mathematics to its applications.

The non creationists are fighting back. http://www.bbc.co.uk/news/education-34921857

I see lots of reports of expensive replacements for the Logitech 16v airplay power supply. http://www.amazon.co.uk/gp/customer-reviews/R1T6H6BFR7IQN5/ref=cm_cr_pr_viewpnt?ie=UTF8&ASIN=B005LNS6WK#R1T6H6BFR7IQN5 Can you please confirm the model number of the speaker and power supply. Also is this 16volts DC or AC (some Logitech devices use an AC supply)? I caution care in replacement because the word seems to be that they are not man enough for the job. If we can tie down the exact requirements we can devise a better alternative.

sciwiz Are you saying that you believe two distinct objects cannot possess the same property? Or perhaps that one object cannot possess more than one property? With all that typing you skillfully avoided responding to my post#83.

Seems to contain all the standard stuff. But before you start to calculate some values in mathematics you need to know some maths to want to have the results. This is where you seem to need strengthening.

So here are some points to consider. There are two groups of red sandstones in Devon. The Old Red Sandstone dating from the Devonian period 400 - 350 MYBP and The New Red Sandstone dating from the Permian / triassic 280 - 200 MYBP They are quite different in character and origin. Sediments range in size from pebbles through grains to fine particles. They get this way through mechanical abrasion and also through grading during transport. The pebbles and grains are usually harder minerals like quarz and feldspar, The fine materials comprise clay minerals, other softer minerals like mica, calcareous material and even organic material. Material of aqueous origin usually has a large mix, wind tends to make all the grains the same size and blow away the dust. The deposited rocks become conglomerates, sandstones, mudstones or siltstones according to the particle sizes. So sandstones are in the middle. So when the mix is being deposited if there is a large percentage of fine material a Matrix is formed with grains and or pebbles included in it. The matrix cements itself together by chemical action (the clay minerals are quite active) and this matrix holds the larger particles, grains and pebbles. Mudstones, siltstones, chalk, limestones and so on are formed in this way. If there is only a small percentage of fine material a Matrix does not form and the grains are first deposited loose. Over time solutions containing cementing minerals work their way between the grains forming the looser sandstones. These minerals are calcite, heamatite (the red in red sandstone), feldspar and some quartzite.

So what is the title of your course?

Since I know nothing about the biological science behind this I am posting the equations here for the benefit of those that perhaps do. It is customary to identify all the variables given symbols I do not know what they are. In particular R and T need defining. [math]{Q_{10}} = \frac{{R_2^{\frac{{10}}{{{T_2} - {T_1}}}}}}{{R{}_1}}[/math] [math]R = \frac{{{{9.5}^{1.41}}}}{{21.5}}[/math] [math]{\log _{\frac{{9.5}}{R}}}\left( {21.5} \right) = 1.41[/math]

Do you mean magnets or magnetic fields? Fields don't have a 'like' and 'unlike'. They are vectors and have a strength and a direction. So they add vectorially. Magnetic vectors in the same direction reinforce, those in the opposite direction weaken the total field where they interact. Magnets have poles that attract or repel, is this what you are really asking about?

1) Practicalities One of the main points made in the original post is the excessive amount of time and effort it take moderating these threads. I see lots of answers here saying that these threads are well controlled so should be allowed to continue. All that these posts are really saying is how hard our mods are working, freely giving their time to do this. But those mods are being squeezed until the pips squeak. We should listen to those squeaks. 2) Wishful Thinking A second commonly expressed hope is that responses here would be able to steer the misguided away from their cherished thoughts. IMHO this is largely wishful thinking; the misguided eventually leave disgruntled, once the mods time has been wasted policing and finally closing their thread, oft going off to report censorship to their contempories. 3)Censorship Banning a subject from the outset and allowing threads to run until they become overheated and then closing them (probably with acrimony) on the opinion of a person or small group of people (nearly) always leads directly to a charge of censorship. This charge may be unfounded and the decision perfectly in accordance with the rules, but the impression taken away is not about the subject matter but about the action. This is why I suggested a mechanically imposed automatic post limit in these threads. No Mod work would be necessary The Poster would have the opportunity to put their point. Responders would have a similar opportunity Tit for tat responding would be curtailed.

The First Law (of Statistics) says Correlation does not imply causation. I think you need to look much more deeply than this.

Not sure I haven't worked it all out, but I was thinking about the relativity of simultaneity and how it is different for for different observers. So points will be included in some observers' set but not in other observers' sets.

You are just playing devil's advocate. Here is a famous (scientific) quote that covers your quibble completely. "Gentleman shall I refuse my dinner because I do not understand the process of digestion?" As I understand the sequence of events Precise measurements of the position of London and New York on the globe were measured in the late 19th century by celestial observations, First the Telegraph and later radio signals provided precise time differences. It was observed that the two continents were separating by a figure a few centimetres per annum. This was very puzzling and disturbing to explain at the time. Around 1910 Wegner came up with his theory of continental drift, and today we have a better one. Is that not the usual pattern of scientific discovery?

How do you know? You Americans thought the Russians weren't going into space but they beat you there. What about the yellow (dark) horse from further east?

Think of lightburst at some arbitrary point in the Universe. Now consider the set of all points illuminated by that lightburst some arbitrary time later. Do the the points included or excluded not depend upon the observer and his velocity relative to the initial point?

Would this imply that the only place in Nature you think mathematics can exist is within a human brain?

I'm glad to hear oceanograhic funding has increased. Some of the Captain Cook's soundings are still on the on charts. However I said space research, not NASA. How much is spent by other organisations, telescopes, satellite coms companies, universities and so on and so forth? Yes some other countries have oceanographic budgets that you appear to count in, thogh Mongolia's is pretty small. Yet you don't want to include the space budgets of other countries. Sure I probably exaggerated for effect, but the usage of and payback from the oceans is vastly greater than that from space.

Sandstones are loosly bound such that when you break a piece the fracture runs through the cement, not the grians of quartz. Metamorphosed sandstone forms quartzite, where the grains fuse together to form large masses of quartz. Breakage of quartzite shears through the quartz particles themselves. UK examples are the Shropshire hills. http://www.alamy.com/stock-photo-devils-chair-a-quartzite-tor-on-stiperstones-shropshire-england-uk-25989467.html

I believe I suggested 5 posts per member responding, not a total length. Isn't there a vigorously enforced policy of not opening another thread on a closed subject?