What is Channel: Definition and 186 Discussions

Channel 4 is a British free-to-air public-service television network with a remit to produce "high quality and distinctive programming". Its headquarters are in London, with a national headquarters in Leeds and creative hubs in Glasgow and Bristol.The channel was established to provide a fourth television service to the United Kingdom in addition to the licence-funded BBC One and BBC Two, and the single commercial broadcasting network ITV.
It began transmission on 2 November 1982, the day after Welsh language broadcaster S4C's launch. Although largely commercially self-funded, it is ultimately publicly owned; originally a subsidiary of the Independent Broadcasting Authority (IBA), the station is now owned and operated by Channel Four Television Corporation, a public corporation of the Department for Digital, Culture, Media and Sport, which was established in 1990 and came into operation in 1993. In 2010, Channel 4 extended service into Wales and became a UK-wide television channel.

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  1. Z

    A Branching ratio for one decay channel

    hi, for studying one decay channel of particle - and measuring its decay width or life time - after this how do we proceed to find the branching ratio - do we need to find the decay width of all possible channel - because its possible even by experiment we are missing some possible decay...
  2. O

    Radio Wave Induced Firing Of Neurons Through Ca2+ Channel Manipulation

    I’ve read that the Ca2+ channels in neurons can be manipulated through the use of certain radio wave frequencies. And the resulting internal/external charge differential will cause the neurons to fire. Does anyone have any more insight into that?
  3. pinball1970

    Stargazing Asteroid filmed over the English Channel

    Quite rare to get one on film so worthy of a thread on its own,"It is just the seventh time an asteroid impact has been predicted in advance. The European Space Agency tweeted that it was "a sign of the rapid advancements in global asteroid detection...
  4. Astronuc

    History History Channel - Recovery of part of Space Shuttle Challenger

  5. MrS

    I Open channel flow: derive function for energy slope on friction?

    I want to determine the normal flow depth in a perfectly horizontal circular conduit. The system characteristics are known (Internal pipe diameter, Mannings roughness, Discharge). However, I am not sure how to calculate the normal flow depth. When using Manning's equation one can find the normal...
  6. Christoffer B

    I Channel electron multiplier as an electron source

    Hi! I'm playing around with a type of electron (and by electron/molecule interactions: ion) source that was briefly touched upon in the 1960's. The basic idea is to use a channel electron multiplier "channeltron" with the anode removed; similar to a single MCP channel. The burst of electrons...
  7. steve1763

    A Derivation of recovery channel for bit flip error

    In general, if R is the recovery channel of an error channel ε, with state ρ, then and according to these lecture slides, we get the final result highlighted in red for a bit flip error channel. I am simply asking how one reaches this final result. Thank you (a full-ish derivation can be found...
  8. D

    How Do You Calculate Static Pressure Drop in a Laminar Flow Channel?

    Hallo. Since I'm new in this field, I hope someone can help me. I have a laminar, steady state, incompressible flow in a channel (a fully developed). Geometry of the channel is on the photo. How should I calculate the drop of static pressure across the channel? Since I have Re, I did calculate...
  9. aladinlamp

    I Open Channel Flow: Dynamics & Forces in Irrigation Channels

    Hi what dynamics are moving liquid in open channel flow without slope (irrigation channels)? Are they mostly hydrostatic forces? imagine 2 scenarios 1. Channels are empty and are being filled for the first time. What forces drive the liquid until it becomes big static lake? 2. Channels are...
  10. F

    Current through Ballistic 2DEG Channel

    So I am a bit uncertain what approach is best for solving this problem and how exactly I should approach it, but my strategy right now is: 1. Solve the time-independent Schrödinger Equation with the given Hamiltonian and find energy eigenvalues of system: -Here I struggle a bit with actually...
  11. S

    I What is the astronomy reason for no UHF channel 37?

    I was reading that the mysterious reason why this channel was removed from public use is because it interfered with radio astronomy (the Wikipedia article didn't mention the reason). So what is going on at this frequency?
  12. D.S.Beyer

    B Value of this 'Science' Channel as quick intro

    I found, what appears to be, a good channel on General Relativity and other science topics. I'm dubious because... the internet. I'd love a second opinion on whether this channels first few videos on The Maths of General Relativity are doing it justice. I'm a dad with a day job and I can't...
  13. V

    Radiation heat transfer in channel flow

    Hi guys, I am confused about the heat transfer mode of between two contacting material, especially in a channel flow. Obviously, conduction or convection dominate the heat transfer process in the process with low object temperature . But I am not sure if I have a fluid of 500 Kelvin, flowing...
  14. R

    Need help- calculating clearing of bubbles from a microfluidic channel

    Hi All, I need some help to figure out how to best go about setting-up and analyzing a micro-fluidics design problem I ran across in my research. It's not the typical single-surface contact angle adhesion kind of analysis. Basically, I have a wide micro-fluidic channel that's formed by a...
  15. S

    Does the brain play a part in Magno and Parvo channel creation

    Regarding human vision and the retina: Where are these channels produced? To put it simply, is it produced in the eye or in the brain. For example; does light enter the eye, hits the retina and it applies a series of filters to produce these 2 different channels (the parvo and magno) and it...
  16. M

    Fluid Oscillating in a Channel CFD

    Hi PF! I'm simulating two fluids, air (blue) and water (red), in a 2D rectangular channel. See picture below: I've turned gravity and viscosity off, and have ##\rho_w=1000## kg/m^3 and ##\rho_a = 0.01## since it cannot be zero. I've also enforced a static contact angle of ##\theta = 71^\circ##...
  17. Zouatine

    Minimizing the area of a channel in contact with water

    My problem: In the solution,our teacher found, that the wet section is minimal if y=L/2 So Am: = L^2 /2; Pm: = 2L; So despite that I try with any value, I can not find a more minimal section, and that's not the case because if I try with y = L / 3 I find Am: L^2/3; Pm: (5/3)*L ; and these...
  18. B

    I Analytical Open Channel Rectangular Fluid Flow

    Hi All, I'm looking for an analytical solution to the open channel rectangular fluid flow profile. The flow is bounded by three walls but the top is open to atmosphere. Assume steady state flow that is parallel and incompressible.I've already found information involving a rectangular flow...
  19. J

    Channel length modulation in a MOSFET

    Hi, I'm struggling to understand how channel length modulation takes place in mosfet. The books n internet said that as drain side is positive, there is less potential difference between positive gate and positive drain, while there is more potential difference between positive gate and zero...
  20. Arslan Siddique

    Calculation of Velocity and Shear rate in rectangular channel

    Hi everyone, I would like to know the formula for calculation of velocity and shear rate in my rectangular fluid channel. Here are the important values regarding my rectangular channel. W= 2.5 mm, H=3 mm, L=35 mm. Fluid: Diluted Bacterial suspension derived from wastewater. Flow rate: 0.125...
  21. J

    A How is the inversion Channel formed in SOI Mosfet?

    Hi, I'm studying MOSFET in detail and I'm struggling to understand how the channel is formed in case of SOI Mosfet. For normal mosfet A positive Gate to source voltage attracts electrons from P substrate towards Gate and thus a channel is formed. But in case of SOI There is a buried Oxide...
  22. R

    Double Channel Wing Plausible?

    Can anyone take a look at the following video, and then look at the attached drawing, and tell me: Why shouldn't the design described in the drawing, improve upon the channel wing lifting force? Here is the video: Here is the drawing:
  23. F

    Momentum equation and open channel flow

    Homework Statement Determine y2 (ft)and v2 (ft/s) using the momentum principle assume widths are the same at 1 and 2 Homework Equations from what i remember in my past fluids class, the momentum equation is: Force = Qvout - Qvin assuming same density and direction However in my lecture the...
  24. K

    Calculating Velocity of Water Flow in Open Channel

    Homework Statement [/B] We have water flowing in an open channel. A small tube is placed in the channel, and the water raises to a height "l" above the water surface. The distance from the water surface to point 1/2 (points are at same height) is d. At point 1 the fluid velocity is V1 and at...
  25. N

    A How to calculate the probability of error in an AWGN channel?

    Hello, I found a paper on the calculation of probabilities of error. However, I didn't know how to plot the graph using equation 3 and 4. These are the list of equations: And this is the graph: I hope that anyone in this forum may guide me to plot this graph. Thank you.
  26. Ekaekto

    Shear rate in rectangular "channel"

    Hi everyone, Non-physics student here, and slightly in over my head :D I am slightly stumped for ideas regarding the calculation of the shear rate in a rectangular type channel, which I need to effectively simulate a blood flow type condition in a channel that has to be rectangular due to the...
  27. brainbaby

    RF Tuner: Adjacent Channel Interference Rejection Filters

    Hi guys The IF section of both monochrome and colour receivers must include rejection filters to suppress adjacent channel interference... Why exactly so, since the work of rf tuner in television receiver is to select a particular channel and as the required channel is selected it then passes...
  28. Joppy

    MHB Surface of protein channel in membranes

    Do we know roughly what the surface of a protein channel looks like? In most of the diagrams they are depicted as a sort of cylindrical tube with a smooth surface, but I'm curious if there are some more detailed documentations somewhere? For example I know they aren't rigid objects and may be...
  29. F

    Does alpha channel really need 8-bits?

    Hi, I am looking for the differences between 16-bit, 24-bit and 32-bit colors for a while. I saw that actually 32-bit color is also like 24-bit color but plus 8-bit alpha channel. Since 8-bit information represents 256 possible values for each color channel, what does 8-bit do exactly for alpha...
  30. M

    Which software do you recommend for capillary channel flow?

    Hi PF! I'm trying to model a fluid dynamics problem where there is flow in a wedge. Length scale is 160mm and two fluid phase: air sits on top of silicone oil. Boundary conditions can be to specify height conditions, flow rate, et cetera. Very low gravity, so surface tension is very relevant...
  31. B

    Velocity in microchannel with temporal temperature variation

    a microchannel of length 2L and width h in the thermal cycling region. the temperature profile ...(1) the cyclic temperature profile leads to a time dependent density ...(2) using the mass conservation equation i.e. ...(3) and momentum balance equation i.e. ...(4) we have to find the exact...
  32. Q

    I Shear Rate in a Rectangular Channel

    Say you have a rectangular channel with a width, w (m), and a height, h (m) and an infinite length. The channel itself is fixed and none of the sides can move with respect to one another. If you know the volume flow rate, V (m3/s) of fluid through the channel, how do you calculate the shear rate...
  33. M

    Struggle to fix a 36W dual channel LED driver

    Good morning and my compliment for their infinite knowledge contained in this forum. I'm struggling to keep being my girlfriend's hero. I have here a nail led 36w UV led lamp that failed last week. Bulbs are tested all ok and connected in two channels each channel in series of 9 LEDs of 2w...
  34. F

    Flow thru a channel constriction

    Homework Statement When a part of the channel is constricted , why will the Emin = Eo ? Homework EquationsThe Attempt at a Solution I just have the figure showing in case 1 and case 2, Emin = Eo without any explanation ... Can someone explain about it ? I tried to search many online resource ...
  35. jedishrfu

    Einstein Biography on National Geographic Channel

    For those of you interested in the racier side of Albert Einstein National Geographic Channel has started a series on it: https://www.theguardian.com/tv-and-radio/2017/apr/24/genius-review-geoffrey-rush-impresses-as-an-unexpectedly-racy-Albert-einstein I've yet to see it but would be...
  36. BillTre

    A Sudden Glacial Outflow Formed the English Channel

    Similar to the bursting of a dam holding back glacial lake Missula which created a deluge that scoured eastern Washington State and created the Columbia River Gourge, a Glacial lake in the area of the North Sea may have spilled out (twice) over a land bridge connecting England to France and...
  37. A

    A What Happens When Particles Travel in Non-Crystal Directions?

    Can someone explain this paragraph especially the bold part in simpler language: "If it is not in a major crystal direction or plane ("random direction", Fig. 2), it is much more likely to undergo large-angle scattering and hence its final mean penetration depth is likely to be shorter." full...
  38. Lacplesis

    Reactor Channel Layout: RBMK, PWR, CANDU Comparison

    Hi, help me out with this one , I have wanted to understand this for a long time, I know different reactors have different approaches to active zone design but here I want to understand how the fuel channel of a RBMK reactor works, I know there are types of reactors like BWR in which I assume...
  39. M

    Why can't a channel flow with two immiscible fluids have two maximum velocities?

    Hi PF! I was recently looking at two immiscible fluids in a 2-D Poiseuille Flow with two immiscible fluids of different densities. Let the total distance of the channel be ##L+\epsilon L##, where the dividing line between the two flows is ##L##. I was thinking of the possible flow profiles and...
  40. H

    Fluid acceleration down inclined channel – unsteady?

    1. Can a fluid which is accelerating down an inclined channel with constant acceleration still satisfy the continuity equation for a constant-density fluid? Since the acceleration will be down the slope, in the streamwise direction, then surely ∇⋅U > 0? 2. Assuming that continuity is satisfied...
  41. JasonHathaway

    Generating Ricean Channel using MATLAB

    Homework Statement I want to generate a Ricean channel using MATLAB Homework Equations Assuming that Ω = -30 dB. The Attempt at a Solution I know how to generate a Rayleigh channel using matlab: H = 1/sqrt(2) * ( randn(N,M) + j*randn(N,M) ) But I really have no idea how to do that for...
  42. Anchovy

    A Why lower limits on proton decay lifetimes depend on channel

    If I look at the lower limits on the proton decay lifetime \tau set by, say, Super-Kamiokande, I'll see different lower limits depending on what the proton could decay into, eg. \tau_{min}(p \rightarrow K^{+} \overline{\nu}) < \tau_{min}(p \rightarrow \mu^{+} \pi^{0}) < \tau_{min}(p \rightarrow...
  43. JasonHathaway

    What is the Notation Used in Simulating an OFDM Channel?

    Hi everyone, I'm trying to simulate an OFDM following a few steps, and I'm stuck at the first: The first step: You have a channel with independent zero mean complex Gaussian taps along with exponentially decaying power profile E{|hk|2|}=e-k/3 with k ∈ [0,21] First of all, does this notation...
  44. jedishrfu

    What Science are You? ScienceWars from Science Youtube Channel

    Sharing this funny video from the ASAPScience channel:
  45. F

    Is Flow Rate in Open Channels Affected by Backpressure?

    Homework Statement I was told that the flow rate in open system at 2 points in the pipe system are not the same, is it true?? Homework EquationsThe Attempt at a Solution
  46. J

    Horizontal open channel flow -- Hydraulic jump calculation

    Dear Fellow Engineers I'm having an issues with my calculations. This case concerns a open channel flow that start off being supercritical on the left and turns into subcritical flow after a hydraulic jump. Given: Volume flow rate Q = 0.16m^3/s Width of the channel b = 1m Resulting...
  47. A

    Classical channel vs quantum channel

    I have a hard time understanding what a channel that transmits classical information is in the framework of quantum information theory. My textbook says the following: Let P(ylx) be a classical channel defined by a conditional probability distribution. We define the corresponding quantum...
  48. J

    A signal on a noisy channel is input to a filter

    This is not homework. I am doing old exams so i have the full solution but need help understanding it. 1. Homework Statement A WSS random signal {X(t)}t∈R with PSD S_X(ω) is transmitted on a noisy channel where it is disturbed by an additive zero-mean WSS random noise {N(t)}t∈R that is...
  49. G

    Ion Flow Through a Channel: Current and Charge

    Sodium ion flows a through a cylindrical ion channel --> diameter = 0.85 um and is 5 um long. potential difference b/w the ends of the channel is 225 mV drift velocity = 0.015 m/s in a period of 1 ms, a total of 15*10^6 ions exit the channel a. total charge exiting the channel in 1 ms =? b...