What is Barrier: Definition and 260 Discussions

Traffic barriers (sometimes called Armco barriers, also known in North America as guardrails or guard rails and in Britain as crash barriers) keep vehicles within their roadway and prevent them from colliding with dangerous obstacles such as boulders, sign supports, trees, bridge abutments, buildings, walls, and large storm drains, or from traversing steep (non-recoverable) slopes or entering deep water. They are also installed within medians of divided highways to prevent errant vehicles from entering the opposing carriageway of traffic and help to reduce head-on collisions. Some of these barriers, designed to be struck from either side, are called median barriers. Traffic barriers can also be used to protect vulnerable areas like school yards, pedestrian zones, and fuel tanks from errant vehicles.
While barriers are normally designed to minimize injury to vehicle occupants, injuries do occur in collisions with traffic barriers. They should only be installed where a collision with the barrier is likely to be less severe than a collision with the hazard behind it. Where possible, it is preferable to remove, relocate or modify a hazard, rather than shield it with a barrier.To make sure they are safe and effective, traffic barriers undergo extensive simulated and full scale crash testing before they are approved for general use. While crash testing cannot replicate every potential manner of impact, testing programs are designed to determine the performance limits of traffic barriers and provide an adequate level of protection to road users.

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  1. E

    Two reacting nuclei, maximum distance to overcome the coulomb barrier

    Basically I'm trying to find out how to find the maximum distance between two deuterium nuclei in order to overcome the coulomb barrier, causing them to fuse. Thanks
  2. C

    Coulomb barrier and proton evaporation

    Why is it that neutrons evaporate from nuclei more easily than protons do? Intuitively, since protons are electrostatically repelled (in addition to whatever nuclear forces they have in common with neutrons), one would expect protons to be ejected more readily than neutrons. (Maybe this is...
  3. C

    Laser Guidance, Maglav Wagon, Wifi barrier

    Hey all! I am gearing up for next year to do a senior project, I want to knock it out in my spare time for the next 10 months. Ideas are: 1) Laser guided missile- 2 phase motor, one to go up then again to go to 'lazed' target. 2) Wifi barrier- setup focused jammers to create a 'wall'...
  4. J

    Potential Barrier help starting problem

    Homework Statement Infinite Potential Barrier particle moving in one dimension is incident upon a potential barrier given by V (x) = Gδ(x) where δ(x) is the Dirac delta function and G is a constant with units of energy times distance. (The delta function must have units of inverse distance...
  5. J

    Sound attenuation barrier height (trigonometry)

    Homework Statement http://img543.imageshack.us/img543/4598/photosfr.jpg Find dss, dsr and thus hs. Homework Equations trig The Attempt at a Solution dss = hs/(sin[θ]) dsr = hs/(sin[∅]) dss = 3.059/(cos[θ]) dsr = 47.191/(cos[∅]) θ = arctan(hs/3.059) ∅ = arctan(hs/47.191) I have tried...
  6. D

    Solving Coulomb Barrier Penetrability with a Confusing Formula

    Homework Statement There isn't an exact problem I'm struggling with, it's one small part of a larger problem, which involves finding the probability protons will penetrate the Coulomb barrier. I'm trying to understand an example in my notes, and the bit that confuses me is attached as an...
  7. E

    Schottky Barrier: Understand Electron Movement

    Schottky barrier ! ? hi all something i can't understand in the schottky barrier diode i know that when electrons move from semiconductor(n type) to metal a depletion region appears in the n side so potentail difference is created so for electrons to move from S.c to metal they need to...
  8. L

    What is the barrier that keeps in molecules?

    There is the atmosphere that is composed of 4 parts: the troposphere, the stratosphere, the mesosphere, and the thermosphere. I know that air is a gas made up of molecules. And a gas fills up the container it is contained in, which is the atmosphere. 1Most of the mass of molecules are in the...
  9. sunrah

    Thermodyn.: ideal gases in 2 two chambers separated by a sliding barrier

    Homework Statement Two different ideal gases are separated by a sliding barrier that can move vertically. The gas in the upper chamber 1 has n moles of material, whilst the gas in the lower chamber 2 has 3n moles of material. At T0 the weight of the barrier is such that the volumes of the two...
  10. Y

    Who does or sees an experiment on rectangluar potential barrier?

    In QM textbook, there is the solution of shroedinger Eq. on the rectangular potential barrier. The reflection rate can be caculated in each case, E>V0, E=V0 and E<V0. But, I can't find the experiment on the rectangular potential barrier anywhere. Is there anybody who does or sees such an...
  11. R

    Potential Barrier (quantum mechanics)

    Homework Statement I need help with part (iii) and (ii) of the follwoing problem: http://img228.imageshack.us/img228/516/79620850.jpg Homework Equations From my notes transmission coefficient for E<U is: T(E)= \left[ 1+\frac{1}{4} \left( \frac{U^2}{E(U-E)} \right) sinh^2 (\alpha L)...
  12. B

    Barrier in an infinite well

    Hello people, I'm trying to plot probability distributions from the given potential numerically. These are the results (particle coming from the right) https://fbcdn-sphotos-g-a.akamaihd.net/hphotos-ak-prn1/s720x720/546478_516459578368236_1799346634_n.jpg What I want to know is why does...
  13. U

    PN junction diode barrier potential attracted to free electrons or holes?

    I am wondering about the barrier in PN junction diode.Due to diffusion negative ions are formed on the P side and Positive ions are formed on the N side of the diode.both opposite sides exert force of attraction and so a line of positive ions and negative ions align along the junction. The...
  14. bayan

    Barrier Tunneling Probability (Proton)

    Homework Statement A proton's energy is 1.30 MeV below the top of a 14.0 fm-wide energy barrier, What is the probability that the proton will tunnel through the barrier? Homework Equations η=\frac{\hbar}{\sqrt{2m(U_{0}-E)}} P_{tunneling}=e^{\frac{-2w}{η}}The Attempt at a Solution I have...
  15. P

    Half-lives and the Fission Barrier

    I could use a basic explanation of how half-lives are associated with the fission barrier. Are half-lives still present in induced fission and not just spontaneous fission? Thanks
  16. Drakkith

    Scientists See Solution to Critical Barrier to Fusion

    Interesting. According to the following link: http://www.sciencedaily.com/releases/2012/04/120423143128.htm What do you all make of this?
  17. C

    Dielectric Barrier Discharge Plasma Discharge Circuit

    To anyone that can help me, Hello everyone. I am student from Mechanical Engineering and I am very new to electronic field. I currently doing my final year project which is developing the high voltage discharge circuit for the DBD plasma. The middle electronic elements is the representative...
  18. J

    Description of a wave packet incident on a square potential barrier

    A wave packet of mean energy E0 is incident on a potential square barrier. The figure below shows stills from a film showing 9 successive stages in interaction. a) True or false? The incident packet at time t = 0 describes many particles, each in a different momentum state. If false, tell...
  19. K

    Can Objects Travel at the Speed of Light?

    I am not an expert on Physics and have for the past year been engulfed in work, so I am very rusty. I read a comment online recently that essentially said the laws of physics simply prevent any object from accelerating to the speed of light (infinite energy required?), but do not say that an...
  20. A

    [Quantum mechanics] Step barrier |R|^2 and |T|^2

    Homework Statement There is a step barrier at x=0, V_0 > E I am given: ψi = e^i(kx−ωt) ---> ψr = R e^i(−kx−ωt) <--- ψt = T e^(−αx−iωt) ---> Part of question I am confused about: State the two boundary conditions satisfied by the wave function at x = 0 and hence find...
  21. D

    Calculate thickness of barrier for tunneling effect

    Homework Statement 2. The tunnel effect predicts that electrons can "tunnel" through an energy barrier that classical mechanics predicts to be impenetrable. In a suitably fabricated “quantum dot” device, a thin energy barrier may be penetrated in this way. If the barrier is 0.2eV in height...
  22. S

    Probability current inside the barrier of a finitie square potential well

    if ψ=C*e^(kx) + D*e^(-kx) show that the probability current density is Jx=(i*k*hbar/m)[c*conj(D) - conj(C)*D] since Jx= (i*hbar/2m)*[ψ * derivative of conj(ψ) - conj(ψ)*derivative of ψ] ψ=C*e^(kx) + D*e^(-kx) conj(ψ)= conj(C)*e^(-kx) + conj(D)*e^(kx) ψ ' = C*k*e^(kx) - D*K*e^(-kx)...
  23. O

    Schottky barrier Rectifying characteristics

    Hello, A Schottky barrier is said to have rectifying characteristics, which from what I can understand is bad ...but would the rectifying characteristics mean that current passing through the junction would be flat ...level is probably a better way to describe it rather than flat. I only...
  24. I

    Energy Diagrams Schottky Barrier Book

    I am looking for a book that explains how a Schottky barrier is formed at a semiconductor metal interface. I have found the attached diagram in a source that i cannot see the references for. Does anyone know of a book containing such a diagram and an explanation of the formation of a Schottky...
  25. B

    Finding Q values of decays and finding distance where Coulomb Barrier = Q value

    Homework Statement 224Ra --> 220Rn + \alpha 224Ra --> 212Pb + 12C 224Ra --> 210Pb + 14C Calculate the Q-Values (in MeV) for these decays given their atomic mass excesses (in MeV) are 88225Ra = 18.818 86220Rn = 10.604 82212Pb = -7.557 \alpha = 2.425 82210Pb = -14.743...
  26. S

    Fermi level de-pinning & Schottky barrier

    Hello. I was womdering does anyone know any good resources of information on Fermi level de-pinning & Schottky barriers? I have been hunting around online, with not much luck. I thought someone here might be able to suggest some things. Thanks. Seán
  27. N

    Double barrier potential in electrical field with matlab

    Hello there :), I have a problem in calculating transmission probability through double barrier potential in electrical field with matlab. While doing some exercises form http://www.nextnano.de/nextnano3/tutorial/1Dtutorial_Transmission_NEGF.htm, I came to the last one, where external field is...
  28. A

    Calculation of ion flux across potential barrier

    Hello! As far as I know, the Eyring equation is used to calculate the speed of a reaction: k=\frac{{k}_{b}}{h} {e}^{\frac{-\Delta G}{RT}} In my course the teacher used this formula to calculate the flux of a species of ions across a barrier of potential, but I didn't understand very...
  29. fluidistic

    Potential barrier in QM problem with coefficient of transmission

    Homework Statement I'll try to recreate from my memory the problem we've been assigned on a test more than one month ago. They gave the solution but I either misunderstood or miscopied it. An electron with kinetic energy 5 eV goes from a region with potential V_0=6 eV (let's call this region...
  30. T

    Particle Tunneling/ Barrier Potential

    1. Show that as the height of the barrier approaches the electron's incident kinetic energy E an approximation to the transmission that includes just a (the barrier width) and the wave number of the incident electron k=((2mE)^1/2)/(h/2pi) can be obtained. The expression has no Vo term. (Hint...
  31. fluidistic

    Quantum mechanics, potential barrier

    Homework Statement A particle of mass m goes toward the unidimensional barrier potential of the form V(x)=0 for x\leq 0 and a\leq x and V(x)=V_0 for 0<x<a. 1)Write the corresponding Schrödinger's equation. 2)Calculate the transmission coefficient for the cases 0<E<V_0 and E>V_0. Hint: Check...
  32. D

    Barrier Deformation and Impact of Car

    Homework Statement Force exerted on a car by a crash barrier as the barrier crushes is F=-(4.5+140s) kN where s is the distance in metres from the initial contact. If a car of mass 2000 kg is traveling at 100 km/h when it hits the barrier the barrier deformation required to bring the car to...
  33. C

    Overcoming the Coulomb Barrier: Energy Requirements

    How much energy particles must have in order to overcome the Coulomb Barrier? Or the correct way to ask this is how much temperature is required for this?
  34. F

    Sudden barrier removal to half harmonic oscillator

    Homework Statement A particle is in the ground state of a half harmonic oscillator (V=m/2 w^2 x^2 x>0, and infinity x<0). At t=0, the barrier at x=0 is suddenly removed. Find the possible energy measurements as a function of time and the wavefunction for all times. Homework Equations <H>...
  35. A

    Proton Collision and Coulomb Barrier

    Homework Statement What temperature would be required for two protons to collide if quantum mechanical tunneling is neglected? Assume that nuclei having velocities ten times the root mean square (rms) value for the Maxwell-Boltzmann distribution can overcome the Coulomb barrier (which you can...
  36. G

    Rectangular Potential Barrier Where E=V0

    Homework Statement V(x) = 0 for x < 0; V0 for 0 < x < a; 0 for x > a Particle of mass m E=V0 Asks for general solution and transmission coefficient. Homework Equations Time-Independent Schrodinger Equation The Attempt at a Solution I've found region I (the left region where x <0) to be...
  37. M

    Light speed barrier / closing speed

    This is something that has always bugged me about relativity... I must be missing something... Lets say you have a space station sitting stationary out in space... a spaceship approaches it from one side at .75c...another ship approaches the station from the other side, also at .75c, still no...
  38. K

    Aplha particle tunneling through coloumb barrier

    Homework Statement Let us approximate the Coulomb barrier of a heavy nucleus by a square potential with a height of V0 = 14.8 MeV and a width of L = 13.7 fm. What is the probability that an α particle with an energy of 5.70 MeV will tunnel through this barrier? Homework Equations...
  39. L

    Tunneling effect or barrier penetrability

    The wavefunction associated with a free particle must be continuous at the barrier and will show an exponential decay inside the barrier. Why it shows an exponential decay inside the barrier? After coming out of the barrier, there is reduced probability for the particle. When there is no loss of...
  40. Y

    About cosmological quantum rectangular barrier potential

    Suppose that one electron from the end of the universe is emitted to the quantum rectangular barrier potential whose size amouts to galaxy size. This belongs to step potential problem or rectangular barrier potential problem? The textbook on Quantum mechanics doesn't deal with the case...
  41. J

    Barrier and Tunneling Problem

    Homework Statement A 1.1 eV electron has a 10-4 probability of tunneling through a 2.4 eV potential barrier. What is the probability of a 1.1 eV proton tunneling through the same barrier Homework Equations eq 1) T= [1 + V02 sinh2(kL)/4E(V0-E)]-1 or if (kL)>>1 we use eq 2) T=...
  42. M

    Transmission and reflection coefficients for potential barrier

    Homework Statement An electron with kinetic energy 5 eV (8.01E-19 J) passes through a 3 eV (4.806E-19 J) potential barrier. There are certain widths for this potential barrier in which the transmission probability will equal one hundred percent and the reflection probability will equal zero...
  43. B

    Why does time dilation create a velocity barrier but not a density barrier?

    Please explain to me what I'm missing: You can't go faster than the speed of light, because of time dilation. The faster you go, the slower time moves for you as compared to objects at rest, and time would stop for you if you ever went the speed of light. That's what makes C the universal...
  44. P

    Schottky Barrier Band Diagrams

    Dear All I am having problems with how to draw band diagrams with band bending for Schottky Barriers and PN junctions. My issue is that I don't know how you determine which Fermi level remains fixed at its equilibrium level and which Fermi level moves to align with it when the two materials...
  45. O

    Potential barrier of Silicon Diode

    As we know the potential barrier of silicon diode is 0.7V at "Normal Temperature" But if the Temperature is 120 degree Centigrade then what will happen? 1) the Potential Barrier will increase 2) Decrease 3) Remain Same Please Explain also!
  46. X

    Infinite potential barrier question.

    Homework Statement I'm asked to calculate the reflection and transmission coefficients for scattering from a potential energy barrier. The potential energy barrier is, V(x)=\frac{\hbar^2}{2m} \frac{\lambda}{b} \delta(x) where \delta (x) is the Dirac delta function. Homework Equations See...
  47. S

    Transmission coefficient in a barrier penetration.

    An electron having total energy E=4.46 eV approaches a rectangular energy barrier with U=5.02 eV and L=949 pm. Calculate this probability, which is the transmission coefficient. I thought this would be an easy one, given that T=e-2GL and G=\sqrt{\frac{2m(U-E)}{H}} where H is the...
  48. P

    Solving Quantum Mechanical Potential Barrier Problem

    Hi! I'm struggeling with a quantum mechanical problem. Homework Statement An alpha-particle is "trapped" inside a uraniumcore, and the potential is simplified to 0 for R2 < r V0 for R1<= r <= R2 0 for 0<= r < R1 I have calculated the transmission coefficient T =...
  49. I

    What is the unidimensional case of a finite barrier inside a finite well?

    After hours searching the web I was not able to find the unidimensional case "a finite barrier inside a finite well". I would appreciate if someone could give me a reference about it.
  50. D

    Quantum Tunneling Across a Square Barrier

    Homework Statement Two copper conducting wires are separated by an insulating oxide layer. This layer acts as a square barrier of height 10 eV. Estimate the transmission coefficient for penetration by 7 eV electrons (a) if the layer thickness if 5 nm and (b) if the layer thickness is 1 nm...
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