What is Delta: Definition and 1000 Discussions

A river delta is a landform created by deposition of sediment that is carried by a river as the flow leaves its mouth and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or (more rarely) another river that cannot carry away the supplied sediment. The size and shape of a delta is controlled by the balance between watershed processes that supply sediment, and receiving basin processes that redistribute, sequester, and export that sediment. The size, geometry, and location of the receiving basin also plays an important role in delta evolution. River deltas are important in human civilization, as they are major agricultural production centers and population centers. They can provide coastline defense and can impact drinking water supply. They are also ecologically important, with different species' assemblages depending on their landscape position.

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  1. F

    Why do integrals featuring Dirac deltas equate to certain values?

    Homework Statement Having trouble understanding dirac deltas, I understand what they look like and how you can express one (i.e. from the limiting case of a gaussian) but for the life of me I can't figure out why the results of some integrals featuring dirac deltas equate to what they do...
  2. U

    Derivatives in 3D and Dirac Delta

    For a research project, I have to take multiple derivatives of a Yukawa potential, e.g. ## \partial_i \partial_j ( \frac{e^{-m r}}{r} ) ## or another example is ## \partial_i \partial_j \partial_k \partial_\ell ( e^{-mr} ) ## I know that, at least in the first example above, there will be a...
  3. D

    Why can't there be an antisymmetric excited state in a delta function potential?

    I have a potential which is zero everywhere except at -2a , -a , 0 , a , 2a on the x-axis where there is an attractive delta potential at each of the 5 points. I know there is a maximum of 5 bound states. I know there can be no nodes for |x| > 2a and a maximum of one node between each delta...
  4. K

    How do you integrate dirac delta functions?

    Homework Statement ∫δ(x3 - 4x2- 7x +10)dx. Between ±∞. Homework EquationsThe Attempt at a Solution Well I don't really know how to attempt this. In the case where inside the delta function there is simply 2x, or 5x, I know the answer would be 1/2 or 1/5. Or for say δ(x^2-5), the answer would...
  5. B

    Delta and Wye Elements wired in parallel

    I manufacture heating elements and a customer wired a delta heater in parallel with a wye heater. They claim that this lowers the overall resistance of the delta thus causing this element to draw more amps than what it was designed for. I disagree and do not see how the heater is eternally...
  6. ognik

    MHB Show δn = (sin nx) / (pi x) is a delta distribution

    Given: Assume that f (x) is continuous at x = 0 and vanishes as x→±∞. Hint. Replace x by y/n and take lim n→∞ before integrating. I apply the hint and get $ \frac{1}{\pi}\int_{-\infty}^{\infty} \,{\lim_{{n}\to{\infty}}}{\frac{sin y}{y}} \,dy $ For the limit, as n -> ${\infty}$ , y -> 0. By...
  7. D

    How to make a delta function signal in a circuit?

    Basically I want to test my analog circuit using a forcing function that has a form of a delta function. The function generator I use outputs sine wave, triangular wave and square wave (+ve and -ve output in one period). Are there any ways to produce a square wave that has an output for like 5%...
  8. entropy1

    Is the Kronecker delta linear?

    I don't see how the kronecker delta function is linear, and hence I don't see how it can serve as a dual basis for a ket space. How is the kronecker delta linear? How can it serve as a dual basis?
  9. G

    ODE with Dirac Delta and conditions at infinity

    I'm trying to solve the following equation (even if I'm not sure if it's well posed) \partial_{x} \, y(x) + a(x)\, y(x) = \delta(x) with ##\quad \lim_{x \rightarrow \pm \infty}y(x) = 0## It would be a classical first order ODE If it were not for the boundary conditions and the Dirac...
  10. anorlunda

    Does Electron Entanglement Affect Total Energy?

    I feel like a ping pong ball on the question of whether or not total energy of a pair of electrons changes when they become entangled or disentangled. I began with a mental model similar to electrons in orbitals. Emit a photon and drop into a lower energy state until reading the ground state...
  11. N

    Limits: 9-x as x Approaches 4 = 5

    lim(9-x) as x->4 = 5 I thought I was supposed to do this: 9-4=5 5=5 But apparently I was supposed to use delta and epsilon? I'm not sure how to find either of these. I know you find epsilon first but I'm really confused so if anyone knows just HOW to find it, that would be extremely helpful...
  12. N

    Finding Delta for a Given Epsilon and Limit: 3-2x, x0=3, E=.02

    Given a function f(x), a point x0, and a positive number E (epsilon), write the limit then find delta>0 such that for all x 0< |x-x0| < delta -> |f(x)-L| < E f(x) = 3-2x, x0=3, E=.02 Here is my attempt: Lim (3-2x) as x->3 = -3 -.02 < |3-2x - 3| <.02 -.02 < |-2x| < .02 .01 > x > -.01 -2.99 > x-3...
  13. N

    When people help they are not allowed to include answers?

    The website rules say that when people help they are not allowed to include answers? But how am I supposed to check my answers... anyone else have this problem?
  14. N

    Can Science Explain the Phenomenon of Greeting?

    Hello
  15. D

    Probability distribution, a 1-D dirac delta in n-dimensions

    Hey everybody, I'm an engineering Ph.D. so my knowledge of n-dimensional Euclidean spaces is lacking to say the least. I'm wondering what sort of approach I can take to solve this problem. ##\boldsymbol{1.}## and ##\boldsymbol{ 2. }## I am given a probability distribution for a random...
  16. patrickbotros

    Why is Delta S purely dependent on gases?

    My teacher constantly stresses that 10 moles of a gas going to 11 moles of a gas will ALWAYS cause an increase in entropy (ΔS>0). But why? For example (I know that O2 shouldn't technically be a liquid, but just as an example): 2H2O(g)⇔H2O(g)+(3/2)O2(l)+2H2 It seems iffy to me. We go from...
  17. Legend101

    Integral involving Dirac Delta generalized function

    Homework Statement Evaluate the integrals in the attached image Homework EquationsThe Attempt at a Solution
  18. N

    Difference between Delta particles and protons and neutrons

    I am trying to figure out the difference between Δ0 and Δ- and the proton and neutron since both appear to have the same combinations of up/down quarks. Deltas have isospin 3/2 and spin angular momentum 3/2 whereas protons and neutrons have isospin 1/2 and spin angular momentum 1/2. I'm...
  19. N

    Prove that (|x-1| < delta) implies (|x^2 - 1| < 1/2)

    Homework Statement "Use the given graph of f(x) = x^2 to find a number delta such that..." Homework Equations If ##([\lim_{x \rightarrow a} f(x)] - L)## then there exists an ##\epsilon## such that ##[0 < |x - a| < \delta] \Rightarrow [|f(x) - L| < \epsilon]##. Here, f(x) and ##\epsilon##...
  20. B

    Verifying Duderstadt & Hamilton's Eqs. (4-134) & (4-137) in Nuclear Transport

    Show by direct calculation that Eqs. (4-134) and (4-137) in the textbook by Duderstadt and Hamilton hold, i.e.:(a) ∫ dΩΩiΩj= 4π/3 δij; i,j = x,y,z; 4π(b) ∫ dΩΩxΩyΩz = 0, if l, m, or n is odd. 4π The integrals are over 4π. This is part of the derivation of the diffusion equation...
  21. N

    How to solve for delta S surroundings at standard conditions

    The question asks to solve for delta S surroundings at 298K when 2.49 moles of H2S (g) react. reaction: 2H2S (g) + 3O2 (g)= 2H2O (g) + 2SO2 (g) My problem is that I don't know how to calculate delta S surroundings. So to solve the problem I'm making the assumption that -Delta S surroundings =...
  22. J

    Solving Delta Dirac Integral Homework Statement

    Homework Statement Solve the integral ## \int_0^{3\pi} \delta (sin \theta) d\theta## Homework EquationsThe Attempt at a Solution I can rewrite ## delta (sin \theta) ## as ##\sum_{n=-\infty}^{\infty} \frac{\delta(\theta - n\pi)}{|cos (n\pi)|}=\sum_{n=-\infty}^{\infty} \delta(\theta-n\pi)## So...
  23. K

    Transmission Coefficient through a delta potential

    Homework Statement Consider an uni-dimensional scattering by a delta function at the origin, given by the potential ##V(x) = g \delta(x)##, with ##g>0##. Using the following result, with ##G(x)## being the green function: $$\Psi (x) = e^{ikx} + g...
  24. M

    Proving lim_{x->\frac{1}{10}}\frac{1}{x}=10

    Homework Statement Prove lim_{x->\frac{1}{10}}\frac{1}{x}=10 Homework Equations |f(x)-L|<epsilon, |x-a|<delta The Attempt at a Solution I need to go from 1/x to x, so I applied an initial condition of delta<1/20 \frac{-1}{20}<x-\frac{1}{10}<\frac{1}{20} \frac{1}{10}<x<\frac{3}{10}...
  25. J

    Programming a Delta HMI A Series: Beginner's Guide

    does anyone know how to program a delta hmi a series
  26. rogeralms

    Quantum Mechanics integral for Dirac Delta with abs value

    Homework Statement Break integral into positive and negative, integrate, recombine and simplify and show that it reduces to a real-valued function. (See attachments) Homework Equations See attachments The Attempt at a Solution My solution is not reducing to a real-valued function. Please see...
  27. H

    Engineering Delta and star transformation of AC circuits

    Homework Statement For the balanced three-phase loads shown in FIGURE 3, ZY = (15 + j15) Ω and ZΔ = (45 + j45) Ω. Determine: Uploaded file C1.png (a) the equivalent single Δ-connected load, (b) the equivalent single Y-connected load obtained from the Δ-Y transformation of (a) above, (c) the...
  28. T

    Understanding Kronecker Delta: Why & How?

    I know what is it but I can't figure out the rationale behind it. As in why do we need it? Moreover I don't know how to represent it in terms of kronecker delta. How do you do that?
  29. M

    LTI Systems, Delta Distribution, and more

    Hi, For my math methods 3 course, I am not quite sure which books to use. The course is based on the math methods book by Riley, Hobson, and Bence, and I don't particularly like it. Hence, I am looking for some alternatives. Especially for the Preliminaries section. I had a real hard time...
  30. starchaser2020

    Calculating Delta V for Orbit Change

    A satellite changes its orbit inclined 66° at 260.0 km altitude to a polar orbit at the same altitude. What Delta V was required? ... I am stuck. do I figure it out using: DeltaV1 = |V_transfer at orbit 1 - V_orbit 1| and DeltaV2 = |V_transfer at orbit 2 - V_orbit 2| or is there another...
  31. U

    Ross Elementary Analysis Epsilon Delta Proofs

    Does Ross's book teach and/or use Epsilon-delta proof techniques?
  32. M

    How do I calculate the power in a star to delta transformation?

    Homework Statement Homework EquationsThe Attempt at a Solution a) the question is to transform star to delta ?
  33. U

    Calculus Spivak Calculus on Manifolds and Epsilon delta proofs

    I am currently having some issue understanding, what you may find trivial, epsilon-delta proofs. I have worked through Apostol Vol.1 and ran through Spivak and I found Apostol just uses neighborhoods in proofs instead of the epsilon-delta approach, while nesting neighborhoods is 'acceptable' I...
  34. rajeshputta

    Star, delta, and star&delta motors

    sir, 1)star connection 3ph motor(415V) which load location is suitable? 2)delta connection 3ph motor(415V) which load location is suitable? 3)star&delta connection 3ph motor(415V) which load location is suitable? please support me.
  35. J

    Delta Transformers on Wye Distribution System

    Hopefully this has not already been asked. It would be hard to do a forum search with the right words to find it if it has been already. I am wondering if it is ever possible or common place to generate power in a Wye generation scheme and then connect it directly to a transformer with a...
  36. J

    Dirac delta function proof fourier space

    Homework Statement I am having trouble understanding this: I have a Dirac Delta function $$ \delta (t_1-t_2) $$ but I want to prove that in the frequency domain (Fourier Space), it is: $$\delta(\omega_1+\omega_2) $$ Would anyone have any ideas how to go about solving this problem? I know...
  37. M

    Finding the delta x of a bow and arrow pullback

    Homework Statement Find the delta x of the bow pullback. The weight of the pullback is 45 kg, the speed of the arrow as it shot out was 184mph( i converted that to velocity and got 83 m/s). Homework Equations I'm using K1+U1+W=K2+U2. The Attempt at a Solution I wasn't sure which formulas to...
  38. genxium

    Function whose 2nd order divergence is the Dirac Delta

    Homework Statement This problem came when I was learning the Poisson's equation (refer to http://farside.ph.utexas.edu/teaching/em/lectures/node31.html). when it came to the step to find the Green's function G which satisfies \nabla^2 \cdot G(\textbf{r}, \textbf{r}') =...
  39. G

    Thermochemistry relating delta H and q of surroundings

    Homework Statement Why does ##\Delta H=\pm |q_{surroundings}|##? Homework EquationsThe Attempt at a Solution Exothermic reactions have a ##-\Delta H## but does that mean that ##q## is a ##+q##. Vice versa for a endothermic reaction. I get confused on which sign i should use for which when i do...
  40. RabbitWho

    What is the meaning of Λ in the contingency equation?

    I last studied maths in school 10 years ago and we never used any Greek letters. 1. Homework Statement Talking about contingency in classical conditioning in psychology. The sum is a calculation that people and animals seem to do in their heads to work out the probability that two stimuli...
  41. R

    Finding the Convolution of Two Functions Using the Laplace Transform

    Homework Statement x(t) = cos(3πt) h(t) = e-2tu(t) Find y(t) = x(t) * h(t) (ie convolution) Homework Equations Y(s) = X(s)H(s) and then take inverse laplace tranform of Y(s) The Attempt at a Solution L(x(t)) = [πδ(ω - 3π) + πδ(ω + 3π)] L(h(t)) = \frac{1}{s+2} Laplace Transform inverse ...
  42. J

    Inverter, Atex motors, star, delta

    Dear Friends, I need technical solution for my problem; Specification: I have two motors, type: 1. HCT/ATEX 45-2T-2 (R/MIN=2800), (400V-3,60A), (KW-1,50) 2. HCT/ATEX 45-2T-3 (R/MIN=2860), (400V-5,00A), (KW-2,20) Also, every motor has its own inverter: Inverters are from INVERTEK DRIVES...
  43. L

    Sinc^2 as a delta function representation?

    Hi, it's actually not homework but a part of my research. I intuitively see that: \lim_{t \rightarrow \infty} \frac{sin^2[(x-a)t]}{(x-a)^2} \propto \delta(x-a) I know it's certainly true of sinc, but I couldn't find any information about sinc^2. Could someone give me a hint on how I could...
  44. B

    How Is Delta V Loss Calculated for Spacecraft?

    How do you calculate how much delta v is lost from gravity and atmospheric drag? I've been looking for days but I can't find anything that actually tells me how it's calculated. For example it takes 1.5 km/s - 2 km/s extra delta v for a low Earth orbit because of drag loss, how was that number...
  45. Logan Rudd

    Determining bound states for delta function potential

    I'm working on a problem out of Griffith's Intro to QM 2nd Ed. and it's asking to find the bound states for for the potential ##V(x)=-\alpha[\delta(x+a)+\delta(x-a)]## This is what I'm doing so far: $$ \mbox{for $x\lt-a$:}\hspace{1cm}\psi=Ae^{\kappa a}\\ \mbox{for $-a\lt x\lt...
  46. A

    Question of "min" function from Spivak

    Hi, Suppose you want to prove |x - a||x + a| < \epsilon You know |x - a| < (2|a| + 1) You need to prove |x + a| < \frac{\epsilon}{2|a| + 1} So that |x - a||x + a| < \epsilon Why does Michael Spivak do this: He says you have to prove --> |x + a| < min(1, \frac{\epsilon}{2|a| + 1}) in...
  47. S

    Dirac delta function identities

    hi deoes anyone know any online resource for proofs of Dirac delta function identities and confirming which representations are indeed DD functions Thanks a lot.
  48. C

    Integrating a delta function with a spherical volume integral

    Homework Statement Integrate $$\int_V \delta^3(\vec r)~ d\tau$$ over all of space by using V as a sphere of radius r centered at the origin, by having r go to infinity. Homework EquationsThe Attempt at a Solution This integral actually came up in a homework problem for my E&M class and I'm...
  49. H

    Delta motor behaviour on loss of phase

    Hi all, I am trying to develop a motor protection scheme for the following scenario. There are two 3.3kV 250kW delta connected motors close coupled to a gearbox driving a crusher. Both have separate DOL starters and protection systems. What happens to the motor current in a motor that loses a...
  50. Dethrone

    MHB How Do We Prove the Limit of 1/x as x Approaches 2?

    $$\lim_{{x}\to{2}}\frac{1}{x}=\frac{1}{2}$$ Here is what I have so far: For all $\delta >0$, there exists an $x$ such that $0<|x-2|<\delta $, $|\frac{1}{x}-\frac{1}{2}<\epsilon$ Cut to the chase: $$\frac{|x-2|}{|2x|}<\epsilon$$ I need to bound $\frac{1}{|2x|}$ somehow, and represent it with...
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