What is Contact: Definition and 447 Discussions

Contact dermatitis is a type of inflammation of the skin. Some symptoms of contact dermatitis can include itchy or dry skin, a red rash, bumps, blisters, and swelling. The rash isn't contagious or life-threatening, but it can be very uncomfortable.
Contact dermatitis results from either exposure to allergens (allergic contact dermatitis) or irritants (irritant contact dermatitis). Phototoxic dermatitis occurs when the allergen or irritant is activated by sunlight. Diagnosis of allergic contact dermatitis can often be supported by patch testing.

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  1. C

    Surface area contact with catalyst effect on hydrogen redox

    I have also posted this question here: Relationship between surface area of electrode and reaction rate of hydrogen in fuel cells, but I really need an answer before tomorrow morning so I hope you don't mind me posting it here as well! I am looking at the effects of increasing the surface area...
  2. K

    (Tribology) Can someone explain Contact Curvature Sum to me?

    I am having a hard time grasping contact curvature sums. Can someone give me a link to where there is a guide or a youtube video? or can someone help me here please. Here are the equations: 1/Rx = 1/rax + 1/rbx 1/Ry = 1/ray + 1/rby 1/R = 1/Rx + 1/Ry The question is this: The ball-outer...
  3. Y

    Determining the Acceleration (Two objects in contact)

    1. The problem statement, all variables and given/known data 2 crates, 75kg(crate x) and 110kg(crate z) are in contact and at rest on a horizontal surface. A 620N force is applied on crate x . If the coefficient of friction is 0.15, calculate: a.) the acceleration of the system b.)the force that...
  4. gracy

    Why is H2SO4 used in the contact process for sulfuric acid production?

    I have a doubt please look at this video At time 1:54 to 2:00 and from time 3:24 to 3:29 After looking at video at time i have mentioned ,one will find that H2SO4 is itself used in this process so my question is what's the point in making H2SO4 by this method,as the method itself requires...
  5. W

    Symplectic And Contact Manifolds

    Hi, we know that every contact manifold has a symplectic submanifold. Is it know whether every symplectic manifold has a contact submanifold? A contact manifold is a manifold that admits a (say global) contact form: a nowhere-integrable form/distribution (as in Frobenius' theorem) ## w## so...
  6. gracy

    Are Contact Lenses Safe for Your Iris? A Look in the Mirror.

    Are contact lenses worn on (fully cover)the iris?If yes,then can iris get damaged or at risk in any way while wearing contact lenses?And how iris function is being performed when contact lenses are put on them?
  7. thephysicist

    What happens when two spinning cylinders come in contact?

    If two spinning cylinders with different MoIs and angular speeds and different radii come in contact with each other at the curved surfaces, how to find out the final angular speeds given all initial parameters? There will be a friction acting at the line of contact and perpendicular to it as...
  8. R

    Need a non contact voltage sensor

    In the process of building my ebike I came across problems of measuring current without putting a sense resistor in the power circuit. For that we build a USB based non invasive current sensor which measures current from -100A to +100A. We also did a kickstarter although It looks like not many...
  9. N

    Calculating Pressure from Contact Surface

    Homework Statement The object has a mass of 10 Kg. And it has a contact surface of 25 cm^2. How much pressure do the object apply to surface? Give your answer is Pascals. Homework Equations N The Attempt at a Solution [/B] So, I think I need to divide the mass with with the surface area to...
  10. A

    Exploring Contact Forces: Understanding Collisions and Launching Objects

    I have recently studied collisions, in which one or two bodies are already in motion. I have tried to apply them to cases in which the bodies are initially at rest, like launching or kicking a ball etc, but they do not work. Can you tell me how to google to find them, 'contact force' gives...
  11. M

    Comsol Mechanical Thermal Contact

    hi, can somebody pls help me with the model i have appended to this post? it is a simple thermal mechanical contact problem but i don't know what is wrong about it and why there is some errors in it after computing. thanks
  12. N

    Contact rate between individuals of different probability density functions

    Hi all, I'm interested in obtaining some measure of contact (or encounter) likelihood between two individuals, each is spatially distributed with some probability density function at time ##t## such that, Space use of individual 1 = ##u(\mathbf{x}, t)## Space use of individual 2 =...
  13. W

    Contact Vector Fields. "Flow Preserves Contact Structure?

    Hi All, I am going over a definition of a Contact Vector Field defined on a 3-manifold: this is defined as " a vector field v whose flow preserves the contact structure " . 1) Background (sorry if this is too simple) A contact structure ## \xi ##( let's stick to 3-manifolds for now ) is a...
  14. O

    How does the positive transition sensing contact work

    Homework Statement Draw the time diagram for this PLC ladder Homework Equations The Attempt at a Solution I am trying to understand how does the positive transition sensing contact work. Definition : The positive transition sensing contact has the value 1 if it receives value...
  15. P

    Depletion region in n-type ohmic contact

    Hello every one, Here in below figure we can see an ohmic contact formation between a metal and n-type semiconductor . Here how the N-type semiconductor bands are banded upward ? and what type of depletion charge exists there ?
  16. D

    Rotating rubber wheels made to contact. Find final angular veloctiy

    Homework Statement A solid rubber wheel of radius R and mass M rotates with angular veloctiy \omega_0 about a frictionless pivot. A second rubber wheel of radius r and mass m, also mounted on a frictionless pivot, is brought into contact with it. What is the final angular velocity of the first...
  17. M

    Need Help Determining Math Prerequisites of Contact Mechanics

    Hi, I'm going to be going into 12th grade. I have taken (out of applicable classes): Calculus 1-3 Differential Equations AP Physics Statics Physical Chemistry 1 (Classical Thermodynamics) Currently Taking: Linear Algebra Number Theory Thermodynamics Statistical Mechanics...
  18. Satvik Pandey

    How long the ball remains in contact with the ground when dropped

    Homework Statement A ball of mass 1kg is dropped from a height 1m . Estimate how long the ball is in contact with the ground in seconds ? Details and assumption Simplify the question by modeling the ball as an ideal spring of spring constant 100Nm . Take gravitational acceleration if...
  19. N

    How can teeth be bent without contact forces

    Hi, so by no doubt you came here because of the bold phrase of the question. So to clear things up, this is a serious question,an no ido not believe in supranomral mind powers. This is a pragmatic question, and I am not a delusional person trying to get attention. it concerns my teeth which...
  20. K

    Overlap ratio or axial contact ratio in helical gears

    Hi, I am trying to understand the Overlap Ratio (OR) / axial contact ratio of a helical gear pair. Unlike transverse contact ratio, I am unable to understand OR so easily. What does it mean if the OR is exactly 1? What will happen practically when it goes less than one? Thanks.
  21. L

    Liquid - polymer equilibrium "contact" distance

    Hi everyone, In this paper ( http://pubs.acs.org/doi/abs/10.1021/la962131c ), the authors calculate the surface energy of polymer and the contact angle of various liquids on these polymers using a so-called "liquid - polymer equilbrium contact dsitance". I'm wondering how to calculate such a...
  22. M

    Friction torque vs. contact area

    I promise this isn't homework, it's actually for my research :-P Here goes: When two bodies are in contact and *translate* with respect to each other, there is no dependence of friction on contact area, and Ff = mu*Fn. Now, assume we have a block of wood on a table with mass m and we apply...
  23. Nathanael

    Sliding down a sphere of ice; when do you lose contact?

    Homework Statement "A boy is initially seated on the top of a hemispherical ice mound of radius R = 13.8 m. He begins to slide down the ice, with a negligible initial speed. Approximate the ice as being frictionless. At what height does the boy lose contact with the ice?" 2. The attempt at...
  24. P

    Threaded connection's initial contact modelling using ANSYS workbench

    Hi everyone! I am doing a simulation of threaded connection in ANSYS workbench and have some problem. In this 2D model, the initial make-up is modeled by setting an "initial overlap" (shown in figure 1). This is how I did: - The initial contact between pin and box as "frictional" with...
  25. A

    Help with Contact Mechanics Between two Spheres

    Homework Statement Hello. Me and my partner are in Grade 7, and are currently doing an inquiry project in Math. We were told to take a question, and calculate theoretical probability of both outcomes. In this case, it would be surviving or dying. Our question is: What is the probability...
  26. G

    Weld contact in Ansys Workbench

    Hi, I am new to Ansys workbench. I am doing analysis with simple fillet joint between two plate. I would like to learn about creation of weld joint/connection between plates. Anybody can help me to create such realistic connection. -Gajanan
  27. A

    Projectile impact contact time

    I am interested to know if there is possible to find out the contact time by a colliding object into a plate, given material properties? My object is to find out the pressure on a plate using force acting on an area. What i know: Mass of both projectile and target plate Impact velocity...
  28. Z

    Ansys frictional contact - convergence problem

    Hi, I am writing to you to ask for help. I have a problem with the contact "Frictional". I'll show you screenshots of my settings and program the console errors. Everything will be shown in the screenshots. The problem is that between the beams and the top element and the bottom element is...
  29. shott92

    Moments at contact tyre patch and wheel spindle

    hi guys this is an image of the rear wheel of a push bike going into a corner as well as what i think are relevant forces, i need to calculate the moments or torque at A (the contact patch) and B (the hub centre) this is to calculate the force on the left hand side of the frame and right hand...
  30. K

    Reason to avoid tip contact in gears

    Hi, When I was studying some gear drawings, I found the tip relief given for all the gears. I find the reason that it avoids the contact between tip of driving flank and root side of driven flank. What is the intention of avoiding this condition? What if I don't give a tip relief? Thanks.
  31. craigi

    Regaining Causal Contact by passing Event Horizons

    When an object approaches a particular event horizon, for a distant observer, in its own reference frame it is not destroyed. The distant observer sees the effect of the object's destruction at the event horizon. We resolve this paradox by the fact that the object and observer no longer have...
  32. W

    Dividing Sets in Contact Structures, and Induced Orientations

    Hi everyone, a couple of technical questions : 1) Definition: Anyone know the definition of the induced orientation of a submanifold S of an orientable manifold M? 2)Dividing sets in contact manifolds: We have a contact 3-manifold (M3,ζ ). We define a surface S embedded in M3 to be a convex...
  33. A

    How can I find work, horizontal force, and time contact?

    Homework Statement For a physics project, i need to answer a bunch of questions after conducting an experiment with projectile motion. I have answered most of them. The questions with the work shown are here: http://i.imgur.com/JmYPMC9.png I cannot answer number 10 and 11, because I don't...
  34. K

    Contact stiffness (Cɣ) in gear.

    Hi, When I discuss about gears NVH, the term contact stiffness(Cɣ) comes across very often. It is given with a nominal mean value with its upper and lower fluctuation. I can thus understand that the stiffness varies from the start of mesh till end of mesh reaching the mean value at it's pitch...
  35. H

    Can a converging lens become a diverging lens in liquid?

    Homework Statement (a)Can a converging lens be made to diverging if it is placed into a liquid? (b)What if?What about a converging mirror? Homework Equations Homework Equations The Attempt at a SolutionThe Attempt at a Solution (a)Let the focal length of the converging lens be...
  36. K

    Are there any material that contact with water and expand?

    Are there any material that contact with water and expand? I can think of sodium polyacrylate, but I can't use it. Thanks.
  37. A

    Solving ANSYS Contact Problem for FEA of Rail Fastening Systems

    I'm currently writing my thesis on a "Finite Element Analysis of rail fastening systems under dynamic load", and I'm using ANSYS Workbench 14.0 for that matter. I don't know how to define the contact area for the clip and the angle guide plate, since it will be changing over time as the clip...
  38. R

    Ground force applied to wheel in pure rolling motion at contact point

    Homework Statement Suppose a wheel with radius R is resting on a non-inclined surface. A torque \tau is applied to the wheel center. In an attempt to prevent wheel from spinning, the ground applies a static friction force to the wheel at the contact point (parallel to the surface), then the...
  39. W

    Is the Dual of a Reeb field a Contact Form?

    Hi, All: Let X be a Reeb vector field, and let ω be a 1-form dual to X. Is ω necessarily a contact form? I know if we have a contact 1-form θ , and Zθ is the Reeb field associated with θ , then from the definition of Reeb field, we have θ (Zθ)=1, which mostly means that θ is...
  40. ckirmser

    Calculating HZ for Contact Binary Systems

    Hello, group! I'm wondering how to calculate the HZ for a contact binary system. Obviously, you can't use just one of the elements, so I wondered how their temperatures would add together. I figure it's not straight addition and I figure it's not just the hotter of the two. Is there a...
  41. E

    Friction in a contact between a pulley and a string

    Homework Statement I need to find a formula for the friction in the system. I had a disk and a pulley connected to a rotation sensor on each side. I wrapped a pulley with a string and there was a small mass attached to the bottom. As I let that mass fall, it would fall and spin a pulley...
  42. B

    Causal contact from opposite sides of Universe?

    Homework Statement No math required, mostly just a conceptual question. Consider two points at direct opposite sides of the expanding visible universe. Could these two points ever been in causal contact? Homework Equations The Attempt at a Solution I take causal contact to mean...
  43. L

    Dry Contact: Definition, Examples, & More

    I am confused about dry contact. Does it mean dry contact vs wet contact as in mercury switch vs regular relay. Any circuit examples. Are transistor switches also referred to as dry contacts. Is a NPN transistor with open collector output also referred to as dry contact?
  44. Q

    Acceleration of point of contact

    For a sphere undergoing pure rolling on a smooth surface with center of mass having constant velocity,what is the acceleration of point of contact
  45. S

    Three blocks are in contact with each other on a frictionless horizont

    Homework Statement Three blocks are in contact with each other on a frictionless horizontal surface. A 503 N horizontal force is applied to the block with mass of 2.6 kg as shown in the figure below. The acceleration of gravity is 9.8 m/s^2. What is the magnitude of the force between the block...
  46. W

    Reeb Fields and Contact Fields.

    Hi again: I'm curious as to someone understands well the difference between a Reeb Vector Field and a general Contact field; a Contact field is one whose flow (even when only defined locally, i.e., in non-complete manifolds) preserves the contact structure, but not the form, i.e., if C is a...
  47. W

    Finding Reeb Vector Fields Associated with Contact Forms

    Hi, All: Let w be a contact form , say in ℝ3, or in some 3-manifold M i.e., a smooth, nowhere-integrable 2-plane subbundle of TM. I'm trying to see how to find the Reeb field Rw associated with w. My ideas are: i) Using the actual definition of the Reeb field associated with a contact...
  48. Superposed_Cat

    Antimatter Why does it annhiliate on contact with ordinary matter?

    why does matter release all its energy upon contact with the opposite charge? Hows does charge bind the energy into particles?
  49. H

    Induction coils and contact materials

    Hi, I'm using an induction coil to heat up an electrically conductive material within the coil. However, I'm worried that adjacent electrically conductive materials, which are not within the coil will also have see a heating effect, due to induction not thermal transfer. I want to avoid this as...
  50. O

    Contact Pressure Vs Traction Vs Deformation in a wire

    Homework Statement A .1in aluminum wire is being pulled from a coil between 2 1in steel rollers. One roller is fixed to the driving motor while the other roller is loaded with a force to provide traction. What is the maximum force that can be applied before the wire is plastically deformed by...
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