What is Domain: Definition and 741 Discussions

A domain name is an identification string that defines a realm of administrative autonomy, authority or control within the Internet. Domain names are used in various networking contexts and for application-specific naming and addressing purposes. In general, a domain name identifies a network domain, or it represents an Internet Protocol (IP) resource, such as a personal computer used to access the Internet, a server computer hosting a website, or the web site itself or any other service communicated via the Internet. In 2017, 330.6 million domain names had been registered.Domain names are formed by the rules and procedures of the Domain Name System (DNS). Any name registered in the DNS is a domain name. Domain names are organized in subordinate levels (subdomains) of the DNS root domain, which is nameless. The first-level set of domain names are the top-level domains (TLDs), including the generic top-level domains (gTLDs), such as the prominent domains com, info, net, edu, and org, and the country code top-level domains (ccTLDs). Below these top-level domains in the DNS hierarchy are the second-level and third-level domain names that are typically open for reservation by end-users who wish to connect local area networks to the Internet, create other publicly accessible Internet resources or run web sites.
The registration of these domain names is usually administered by domain name registrars who sell their services to the public.
A fully qualified domain name (FQDN) is a domain name that is completely specified with all labels in the hierarchy of the DNS, having no parts omitted. Traditionally a FQDN ends in a dot (.) to denote the top of the DNS tree. Labels in the Domain Name System are case-insensitive, and may therefore be written in any desired capitalization method, but most commonly domain names are written in lowercase in technical contexts.

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  1. R

    Coherence Domain in Living System

    (note: I posted this here instead of the Biology forum because the topic involves heavy quantum concepts that mere biologists can't handle) I read PF Mentor Ryan_m_b mentioned elsewhere that "Discussing quantum effects in biology is not a banned topic on this forum, however threads that...
  2. M

    Tension on a capacitor from Laplace domain to time domain.

    The problem ask me to find the tension on a capacitor after a switch has been opened. I have everything in terms of equations in s-domain and I'm sure they aren't wrong because I checked on the book. My unique problem is to understand a certain passage necessary to find the voltage knowing...
  3. H

    Is this complex set S a domain?

    Homework Statement Let S be the open unit disk of radius 2 centered at the origin. T is a subset of the real axis. The set R is obtained by removing T from S. Is R a domain when: 1. T is the line segment {z\in ℂ | Re(z) ≤ 1 and Im(z) = 0} 2. T is the line segment {z\in ℂ | Re(z) < 2 and...
  4. P

    Value of a measure theoretic integral over a domain shrinking to a single set

    Hi. Under what conditions does the following equality hold? f(x)=\lim\limits_{\Omega\rightarrow\{x\}} \frac{1}{\mu(\Omega)}\int_\Omega f d\mu where \mu is some measure. Being a little more careful, let \Omega_i be a sequence of sets such that \Omega_{i+1}\subseteq\Omega_i and...
  5. F

    Domain & Range of Inverse Function f-1: x≤0, y≤0

    Homework Statement The function f:x→ 4-x2 for the domain x≤0. Find the inverse of is denoted by f-1 and state the domain and range of f-1. Homework Equations Set equation to 0 and solve for x to find inverse. The D and R is going to be switched for the inverse..? The Attempt at a...
  6. J

    Domain of convergence of Puiseux series

    May I ask if it's appropriate to ask in this sub-forum, are there any general methods for computing the domain of convergence for Puiseux series representations of algebraic varieties? I'm unable to find anything on the matter. For example, suppose I'm given the ideal in \mathbb{C}[z,w]...
  7. G

    Domain and range of composite function

    Homework Statement The function f has domain (-∞, ∞) and is defined by f(x) = 3e2x. The function g has domain (0, ∞) and is defined by g(x) = ln 4x. (a) Write down the domain and range of f∘g. (b) Solve the equation (f∘g)(x) = 12 2. The attempt at a solution (a) Is it correct...
  8. T

    Domain of Quadratic Equations

    Hi guys, I'm really confused in finding the domain of quadratic equations. For example: when finding a suitable domain so that an inverse exists, why is the domain of x2-4 x>0 whilst, the domain of 2x2+3 is x≥0 Can the domain of x2-4 be x≥0? Furthermore, what is the largest domain and how do...
  9. M

    Run time error M6201:MATH-log domain error

    hi all, i am getting the above problem while executing my fortran program. please help me how to fix it. thank MNM
  10. Q

    Can I use polar coordinates in a triple integral?

    if i am being asked to write the domain of integration in a triple integral problem in a cartesian form , may i used polar coordinates to express instead of x and y? thank you
  11. D

    Easy Seperable Differential Equation Domain Questions

    This is a problem from the Boyce and Diprima Elementary DE book. I solved this equation and got the correct solution. However, the author notes that the solution is defined on the interval (-2,3) only. I have found it to be defined (-inf,-2)u(-2,3)u(3,inf), or EVERYWHERE BUT x=-2, x=3. Is...
  12. C

    Challenge problem to the community - - - domain and range

    What are the domain and range of the following: (Note: It is a relation that is not a function.) y^2(x^2 - 1) = x^4
  13. C

    What are the domain and range of this relation

    in interval notation? y^2(x^2 - 1) = x^4 (This is my own problem.)
  14. J

    Domain of g(t): All Real Numbers

    Homework Statement Use set or interval notation to give the domain of the function: g(t)=(x-5)/sinx Homework Equations The Attempt at a Solution So looking at this, I recognize that x cannot be 0,180,360, etc... it's just putting this into set or interval notation that...
  15. W

    Interior of Exterior of a looped domain

    The photo below is a picture of a problem in my complex analysis textbook but a topology question occurred while I was reading it. (Just to avoid any confusion, I have not taken a topology class yet.) The problem is asking to compute the integral (at the top of the picture) around the closed...
  16. R

    Filter DC offset - apply High-pass filter (in time-domain or frequency domain?)

    Hello all, I want to filter DC offset for a signal by applying a high-pass filter to it (I've been told that to filter the DC offset this is what I should do - I'm not sure why exactly!) My question is; do I do that in the time-domain or frequency-domain after applying FFT? And I would...
  17. P

    Time/Frequency Domain Contraction/Expansion

    Hey guys, So I'm trying to intuitively understand the conclusion that a contraction in one domain leads to an expansion in the other domain (and vice-versa). Mathematically, I can see how this would happen, e.g., a bandpass filter with -pi/2 < w < pi/2 would result in a narrower time domain...
  18. M

    Solving Heat Equation w/ Neumann BCs Different Domain

    Hi guys! I'm to find the solution to \frac{\partial u}{\partial t} = \frac{\partial^2 u}{\partial x^2} Subject to an initial condition u(x,0) = u_0(x) = a \exp(- \frac{x^2}{2c^2}) And Neumann boundary conditions \frac{\partial u}{\partial x} (-1,t) = \frac{\partial...
  19. D

    Cylindrical Coordinates Domain

    Homework Statement Let W be the region between the paraboloids z = x^2 + y^2 and z = 8 - x^2 - y^2 Homework Equations The Attempt at a Solution for each domain, 0 ≤ z ≤ 8 0 ≤ r ≤ 2 0 ≤ θ ≤ 2\pi So... \int^{2\pi}_{0}\int^{2}_{0}(8-2r^{2})r drdθ
  20. D

    Triple Integral Domain

    1. The problem statement, all variables and given known data f(x,y,z,) = e^{2x-z} W: x + y + z ≤ 1 x, y, z ≥ 0 Homework Equations The Attempt at a Solution For each domain, could you check it please? This is the only triple integral that's haunting me 0 ≤ x ≤ 1-y-z 0 ≤ y ≤...
  21. D

    Spherical Coordinates for a Sphere with Variable Radius

    Homework Statement f(x,y,z) = 1 x^{2} + y^{2} + z^{2} ≤ 4z z ≥ \sqrt{x^2 + y^2} Homework Equations The Attempt at a Solution How can I know ρ if there is z variable? Do I just square root both 4 and z? For θ, since it is sphere it would be 0 ≤ θ ≤ 2\pi right? for \phi, is...
  22. D

    Polar Integration Domain part 3

    Homework Statement f(x,y) = (x^{2} + y^{2})^-2 x^{2} + y^{2} ≤ 2 x ≥ 1 Homework Equations The Attempt at a Solution -4\pi ≤ θ ≤ 4\pi secθ ≤ r ≤\sqrt{2} are these the correct domain?
  23. D

    Domain for Polar Coordinate Part 2

    Homework Statement f(x,y) = e^{x^2+y^2} x^{2} + y^{2} ≤ R Homework Equations The Attempt at a Solution I believe this is a circle. f^{2pi}_{0}^{sqrt(R)}_{-sqrt(R)}e^{x^2+y^2}*r*dr*dθ = f^{2pi}_{0}f^{sqrt(R)}_{-sqrt(R)}e^{r^2}*r*dr*dθ after u substitution... =...
  24. D

    Defining the Domain for a Polar Coordinate Function

    Homework Statement f(x,y) = y(x^{2} + y^{2})^-1 y ≥ \frac{1}{2}, x^{2} + y^{2} ≤ 1Homework Equations The Attempt at a Solution Would you check my domain please? f^{pi}_{0}f^{sqrt(3)/2}_{-sqrt(3)/2} sinθ drdθ
  25. P

    Frequency Domain Analysis - the math

    I am studying Control Theory from Ogata. My math is a little rusty, so this is a math question about Frequency Domain Analysis. Check this page - http://www.flickr.com/photos/66943862@N06/6337116280/sizes/l/in/photostream/ I get everything upto Equation 8-4 However I don't get the line after...
  26. P

    Engineering Solving a circuit in Freq Domain

    Homework Statement Question as in image: Homework Equations The Attempt at a Solution When I did Mesh, I got this: -20j-20Ia+(Ia-Ib)2j=0 (Ib-Ia)2j-(Ib-5)j-(Ib-Ic)50=0 -(Ic-Ib)50-(Ic-5)8j-2(Ia-Ib)=0 2(Ia-Ib)-100Id=0 Ia-Ib=Ix **This is done from Left to Right**...
  27. E

    Every finite domain is a division ring

    I am taking a first course in algebra and I am having issues with a detail in this proof that every finite domain is a division ring. The argument that I used is that (because of cancellation in domains) left & right multiplication by a nonzero element r in a domain R gives a bijection from R...
  28. A

    Find the derivative and the domain of the derivative (trig funtions)

    Homework Statement f(x)=sin(2x+5) Homework Equations I am supposed to find the derivative, and the domain of it. The problem is that I cannot deal with the simplification of it. The Attempt at a Solution As far as I know, I am suppsosed to use f(x+h)-f(x)/h =...
  29. S

    Can two functions have the same frequency domain representation?

    Hi, I stumbled upon the following two functions which have the same freq domain representation, 1/(j.pi.f) 1.signum(t) = u(t) - u(-t) 2. 2u(t) what is the reasoning behind them having the same f domain representation?
  30. A

    Norms and Units of an Integral Domain

    In an example in my algebra text, (from the section on unique factorization domains) it is describing the ring \mathbb{Z}[\sqrt{-5}], and demonstrating that it is not a UFD. It starts by giving the norm N(a+\sqrt{-5}b)=a^2+5b^2. It remarks that if zw=1, then N(z)N(w)=1, and then it goes on...
  31. M

    Continuity of Polynomial Functions in their Domain

    The first hypothesis is that f is continuous on [a,b]... Is there a more concise mathematical way of saying... "because the function f is a polynomial it is continuous in its domain."? Because I rather not write that on my test it looks sloppy and non professional...
  32. K

    Multi resolution Time Domain (MRTD)

    Hi everybody, i am having difficulties to write a program using only MATLAB to solve the Mrtd SCHEME...that is solving the maxwell equations...can anyone please help me
  33. O

    Domain of f(x)= (1/(3+lnx)): (0,∞)

    Hi just a quick question Differentiate f and find the domain of f. (Enter the domain in interval notation.) f(x)=(1/(3+lnx)) Here is my Derive: ((-3+lnx)^-2)(1/x) which is correct And for the domain (web assign wants interval notation) When I was doing this part, I wasn't sure if it...
  34. A

    Positive Set in an Ordered Integral Domain

    "Positive Set" in an Ordered Integral Domain I'm currently reading Durbin's Modern Algebra, and I have a question about the positive set in ordered integral domains. Durbin characterizes an ordere integral domain as one with a subset which is closed to addition and multiplication, and...
  35. K

    What is the Domain of the f(x)^g(x) Function?

    Homework Statement We have to find the domain range (hope I'm using this right) of some functions, one of them being h(x)=f(x)^g(x), say h(x)=(x^2-4)^(x). I've been looking around and couldn't find the domain range of the x^x function, so I am kinda stuck on this one. Homework Equations...
  36. N

    Pspice Problem - How do I take Logarithm_10 in a frequency domain?

    Homework Statement I am simply simulation using a small circuit consisting of a square wave generator, a resistor and a GND. The Voltage varies from 0 to 0.5V and the frequency is 100kHz for the sig-gen. I can simulate and output the transient response, a square wave with the above...
  37. Z

    Domain / range of this function

    Homework Statement I don't remember the exact question right now, but it was something like this: f(x) = sqrt(4 - x^2) I needed to give the domain / range of it, and also symmetry I believe. Homework Equations The Attempt at a Solution I know this is a half circle after...
  38. L

    Finding the domain of a composite function

    Homework Statement I started out with f(x)=sinx and g(x)=1-√x. I found f(g(x)) which is sin(1-√x) and now my problem is how to find the domain. I've really been struggling with the domain part and just need this one done step by step so i have an idea of how to actually do it. Homework...
  39. W

    Rewrite as piecewise + domain + range?

    Homework Statement 1. Rewrite as piecewise: g(x) = 2x - |3x-2| 2. Give domain and equation represented by f(g(x)) when g(x) = √(x+1) and f(x) = 3/x 3. Give range of P(x) = {2x-1, x >/= 1 {x^2 + 1, -1 </= x < 1 {√|x|, x<-1 thanks in advance Homework Equations The Attempt at...
  40. pairofstrings

    Meaning of continuous frequency domain

    Homework Statement Discrete-time transforms What does it mean when it says this : These transforms have a continuous frequency domain: Discrete-time Fourier transform Z-transform What is the meaning of continuous frequency domain..?
  41. A

    Convolution of two delta functions in frequency domain

    Apparently, when convolving, for example: [δ(ω-π) - δ(ω+π)] * (δ(ω+50π)-δ(ω-50π)) the result is δ(ω+49π)-δ(ω-51π)-δ(ω+51π)+δ(ω-49π) where δ() is the Dirac delta function, * the convolution operator and ω the frequency variable How do we get to this? Can you help me on the intuition in...
  42. S

    Averaging in tthe frequency domain

    Hi... I have several Power Spectrua that I want to average into a single representative power spectrum. Then, I have to analize the amplitude spectrum of the average (i.e. sqrt(power spectrum)) Doing that doesn't give the same result as averaging the amplitude spectrums. Supose I have tho...
  43. R

    How to convert time domaine signal into frequency domain signal

    Hi, I am new to signal theory and don't know what is time domaine signal and frequency domaine signal. Please some can explaine me clearly and how can we convert between those two domaines. I read the topic in wikipedia which makes me somepart clear but interested to know...
  44. A

    Jordan-Brouwer Separation Theorem and Invariance of Domain

    So I'm having trouble understanding how these two are related, i.e., how one proves the other. I understand the ideas behind both of them: For J-B, you're basically taking R^n and throwing in a sphere, so the inside of the sphere is bounded and everything outside the sphere is unbounded. For...
  45. Rasalhague

    What is the domain of a die ?

    What is the "domain of a die"? - Haim Permuter: Mathematical methods in communication: http://www.ee.bgu.ac.il/~it09/lec1/lec1.pdf (PDF notes). What is the domain of X, and what is its rule? Is the domain the set of ideas {the concept of the die landing on 1,...,the concept of the die...
  46. D

    Question on maximal ideals in an integral domain

    In an integral domain, I found that the number of maximal ideals in a Notherian ring containing a particular element is finite. If the condition is dropped that the ring be Notherian, can anything like this be said?
  47. Shackleford

    Determine if integral domain or field

    I found the unity to be 1. I'm not sure how to determine 3) for each. http://i111.photobucket.com/albums/n149/camarolt4z28/IMG_20110805_224110.jpg?t=1312602377 http://i111.photobucket.com/albums/n149/camarolt4z28/IMG_20110805_224012.jpg?t=1312602392
  48. D

    Windowing in Frequency Domain: Exploring Effects on Time Domain Data

    Hey @ all, when windowing in DSP in time domain one multiplies all recorded time samples with a weighting factor (hanning, hamming, etc.), followed by a Fourier transform (FFT) to reduce sidelobes in the spectral domain. But now when thinking about starting up in frequency domain where I...
  49. N

    Domain range intervals; if you can

    Homework Statement Hello. Can someon help me understand the difference between these two problems? #1: f(x)+3 #2: f(x+3) The reason I want to know if becuase my question tells me to use the domain of f(x) as [4, 8] and the range as [2, 6] Then it wants to know the domain and range...
  50. R

    How to find Fourier Transform of pulse and apply it on filter response?

    Hi all, I have a filter whose amplitude and phase response in terms of w(omega) is known to me which i calculated numerically. Hence, the value is known only for discrete values of w(omega). Now, I want to know the output which this filter will produce on sending a temporal pulse(pulse in...
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