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    Clustering of azimuths

    Hi all, If I have a set of azimuths, e.g. [ 0, 10, 11, 67, 68, 69, 70, 124, 127, 136, 355]. How can I cluster these directions bearing in mind that 355 is close to 0? Can someone point me to a link, preferably with an algorithm I can use. Cheers
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    Notation for angle wrapping

    Hi I am looking for the proper notation to represent angle wrapping in a mathematical function. For example if I have a function of the form: y=exp(θ) (and θ is an angle in degrees.) How do I write this function to explicitly assert that: -180 ≤ θ < 180 ? So that for example if...
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    Pretty Good Privacy (PGP)

    This is a thread about encrypting your private emails. I put it in discussion as I would be interested to read about people's views on this given the recent revelation that certain governmental agencies are storing all our emails. Does anybody out there encrypt their emails? Or perhaps you...
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    Fortran Fortran bug: rank problem gfortran

    This is my own code, and it won't compile with gfortran. All I want to do is extract the location of the cell with the minimum value in an array. A seemingly simple task but one that does not work with the intrinsic function minloc, for reasons I do not understand. The error message...
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    In which region does my (arbitrary) point lie?

    My problem is that I have a bunch of regions, in this case they are tectonic plates. Each region has a complex boundary, described by polygons, in a text file with co-ordinates. I have a long list of points (>100,000) distributed globally and I need to know in which region each point lies...
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    What causes dispersion?

    A wave travels through a (homogeneous) medium at a given velocity, the velocity depends on the frequency of the energy.... why?
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    Random selection, with skewed distribution

    Hi there, (to mod: not sure where to post this, please move if I've got it wrong) I have a grid of values with 41x161 nodes describing some parameter space. Each node has an associated value, λ, which represents the uncertainty of the parameter choice at that node. I want to make/find an...
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    Generation of plume (in the Earth's mantle)

    I'm wondering if there is a generally accepted mechanism by which a plume is formed and how this then applies to the Earth's mantle, and so-called "mantle plumes". Specifically I am a bit stuck on these questions: Do plumes require a thermal boundary layer as their source? What process...
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    Verhulst equation - integration problem

    Verhulst equation -- integration problem 1. Homework Statement Integrate the unforced Verhulst equation over t from t_{0}-\epsilon to t_{0}+\epsilon, take the limit \epsilon \downarrow 0 and show this lead to the following requirement for the discontinuity in g: \stackrel{lim}{\epsilon...
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    Mantle Geochemistry

    Does anybody have any resources on MANTLE GEOCHEMISTRY as I would like to do some reading. I'm reading Don Anderson's" [Broken], although apparently he has some slightly odd views as to the nature of the mantle's 660 km deep discontinuity. An...
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    A Simple Pole

    1. Homework Statement Why is the pole at z=+i simple for the function 1/(1+z^{2})? 2. Homework Equations The function can be written as: h(z)=1/(1+z^{2})=1/[(z-i)(z+i)] It can be expanded as a Laurent series: h(z)=\sum^{\infty}_{-\infty}a_{n}(z-z_{0})^{n} The function is...
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    Fourier transform help

    1. Homework Statement Show that for a fixed value of \omega that G(\omega)e^{-i\omega t} is the response of the system to the input signal e^{-i\omega t}. (From Roel Snieder's book 'A Guided Tour of Mathematical Methods for the Physical Sciences', pg 233 (Section 15.7, Problem e)) 2...
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    Programs PhD - Read HOW many papers a DAY?

    PhD -- Read HOW many papers a DAY?! How many papers should a PhD student read each day? I'm in my first year. I have been told today that I should be reading 3 papers a day. Previously I was told I should be reading 6 papers a day. On both these occasions I was told by a senior professor...
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    End Permian Mass extinction

    A new hypothesis has emerged in the search for the cause of Earth's greatest ever mass extinction: The Permian-Triassic Mass extinction event (~250 million years ago).
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    New Finding: Light element layer in Earth's outer core

    Researchers have found seismic evidence for a 300 km thick layer in the outer core formed of light elements expelled upon inner core solidification. They believe the gravitational energy released by this compositional convection is a key input to the energy that drives the geodynamo...
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    Solve Differential eq with initial conditions

    1. Homework Statement Solve: \frac{\partial H}{\partial t} = -4\kappa H^{2} With initial condition: H(0) = 1/L^{2} To find: H(t) = \frac{1}{4\kappa t + L^{2}} 2. The attempt at a solution I tried using Taylor series expansion such that: H(t)\approx H(0)+t\frac{\partial...
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    Harmonic Function

    1. Homework Statement Derive that: \left[r\frac{\partial\overline{f}}{\partial r}\right]}^{r=R}_{r=0}=0 2. Homework Equations I have taken the Laplacian \nabla^{2}f=0 for a disk in cylindrical co-ordinates and have found that: \int^{R}_{0}\int^{2\pi}_{0}...
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    Evaluate integral of second order differential

    1. Homework Statement Evaluate \int^{2\pi}_{0}\frac{1}{r}\frac{d^{2}f}{d\varphi^{2}}d\varphi 2. Homework Equations n/a 3. The Attempt at a Solution I get the integral as \frac{1}{r}\frac{df}{d\varphi} Not sure how to evaluate this.
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    Divergence in spherical coordinates

    I am stuck on this problem. Use these equations: \textbf{v}(\textbf{r}) = f(r)\textbf{r} \frac{\partial r}{\partial x} = \frac{x}{r} And the chain rule for differentiation, show that: (\nabla\cdot\textbf{v}) = 2f(r) + r\frac{df}{dr} (cylindrical coordinates) Any help greatly...
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    Evaluating Volume of a Sphere in Cartesian Framework

    I'm trying to sharpen up my maths before I go back to university to start my PhD and am working through Roel Snieder's excellent book 'A Guided Tour of Mathematical Methods for the Physical Sciences'. The problem I am working on is how to evaluate the volume of a sphere in Cartesian...
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    Link between fractals and chaos

    I have studied fractals and think of them as things that exhibit self similarity at different characteristic scales. For example a grain of sand looks a bit like a pebble, which looks a bit like an outcrop, which looks a bit like a mountain. If you count the number of grains of sand there will...
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    Blue Pool - colour change phenomenon

    On the weekend I visited Blue Pool in Dorset, England. This is an old abandoned clay mine that has filled with water to produce an attractive pool. Apparently the colour of the pool constantly changes colour...." [Broken] I didn't observe the colour...
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    A sesimic image of the whole Earth

    Has this been done? I've seen tomographically derived "velocity models" of the earth before. These can show features, such as anomalously fast slabs under continents (subducting plates) and anomalously slow blobs beneath hot spots (mantle plumes). But has anybody ever imaged the Earth with...
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    Dyslexia in the sciences

    Looking back I remember my first science teacher making a lot of spelling mistakes on the board. At uni I noticed that many of my colleagues were dyslexic, and quite a few of the lecturers were too but they were quite good at covering it up. Now I work with scientists and I have been shocked...
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    What are the odds?

    A friend recently observed that Manchester United have been drawn against Aston Villa in The 3rd round of the FA Cup 4 times in the past 7 draws. There are 64 teams in the 3rd round draw. What are the odds of this happening? I believe I have the answer, but I need someone to verify my...
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    E8 - The GUT?

    Hey, have you heard about this? Check it out... An impoverished surfer has drawn up a new theory of the universe, seen by some as the Holy Grail of physics, which has received rave reviews from scientists...
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    Sexing up science

    Do scientists have an image problem? The linked article (below) talks about how the stereotypical white lab coat may be detrimental to the public perception of scientists, is it time for a change?
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    Climate change: the future.

    Oh no, not another global warming thread!!! :surprised But seriously, I read that CO2 accounts for ~20% of the greenhouse effect on Earth, we are undoubtedly raising the amount of this (and other) greenhouse gases in the atmosphere. The greenhouse effect is very important in determining the...
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    Free education from MIT

    Free education from MIT!!! I don't know if this is common knowledge, but MIT have put up a lot of course notes for free access. You just need a pdf reader. Here's the link: It is quite frankly amazing! You can learn anything from maths to linguistics, I...
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    Pulsating Equator

    William Astley said: I found myself wondering about the pulsating equator recently. For those not in the know, Andre presented this excellent nutshell description in a previous". Check out this cool...