Joint Definition and 327 Threads

A joint or articulation (or articular surface) is the connection made between bones in the body which link the skeletal system into a functional whole. They are constructed to allow for different degrees and types of movement. Some joints, such as the knee, elbow, and shoulder, are self-lubricating, almost frictionless, and are able to withstand compression and maintain heavy loads while still executing smooth and precise movements. Other joints such as sutures between the bones of the skull permit very little movement (only during birth) in order to protect the brain and the sense organs. The connection between a tooth and the jawbone is also called a joint, and is described as a fibrous joint known as a gomphosis. Joints are classified both structurally and functionally.

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  1. F

    Physics on its own or a Joint Honours of Physics + Computer Science

    Hi guys I'm new here, looking for advice on what Honours degree to do next year. I left High School at 16 (I am now 23) and have been working in IT for the past 4-5 years, boring IT support kind of jobs. I've been an avid user of Linux(Fedora) for quite some years and have self-taught a little...
  2. J

    Bolted Flange Joints: Studs vs. Bolts

    Hello everyone! Please, help me with the terms. There are bolted flange joints, right? What if there are studs used in this joint? Any change to the name of the joint? Why I'm asking is because in Russian there is difference. Stud bolts or studs are called absolutely different from bolts...
  3. N

    16inch rotatable pipe flange joint

    I am making a dust cleaning system for induction furnaces in my steel mill and for that I have to design a mechanism with which about 7m length of 16inch diameter pipe can rotate about an elbow attached to one end but wihtout any leakages. ANY HELP would be appreciated.
  4. E

    Estimating joint distributions from marginal

    Suppose I have the marginal probability density functions of two random variables A and B, P(A), and P(B). Suppose I modeled P(A) and P(B) using a mixture model from some dataset D and obtained a closed form pdf for each. I am interested in finding their joint density function P(A and B) and...
  5. N

    NE B.S. vs. NE and CHEM E joint major

    Hi, I’m a transfer student to UC Berkeley (fall 12), coming from a community college. I am transferring as a nuclear engineering major, but I can choose to do a joint major program in chemical and nuclear engineering (core courses are taken from both majors). The reason I’m considering the...
  6. U

    MHB Calculating Joint Probability - Get the Answer!

    http://img151.imageshack.us/img151/6002/variance.jpg Just wondering, how did they get the part boxed in blue? Thanks.
  7. R

    Identifying a Joint and Plastic Version in Australia

    Hi, Does anyone know what the name of this joint is? And if possible where i could buy a plastic version in Australia or online? Thanks in advance!
  8. W

    STATICS truss/ math equation - joint by joint

    studying for my test, I have a truss joint equation with 2 variables ƩFx = 0 : 4/15 (15kN) - 10/10.44(Fbd) - 4/5(Fbe) = 0 12 = .957(Fbd) + .8(Fbe) ƩFy= 0 : 3/5 (15kN) - 6kN - 3/10.44(Fbd) + 3/5(Fbe) = 0 6 = 9 -.287(Fbd) + .6(Fbe) -3 = .287(Fbd) + .6(Fbe) this is where I'm...
  9. G

    Question for Truss- method of joint

    Does anyone know how to solve the question below? I have no idea to do it with some missing angle inside the triangle. [PLAIN]http://img267.imageshack.us/img267/374/truss.jpg Shot at 2012-07-01
  10. T

    Limits of Integration for Joint Distribution problems

    Suppose that (X,Y) is uniformly distributed over the regiondefined by 0≤ y ≤ 1-x2 and -1≤ x ≤ 1. a) find the marginal densities of X and Y Attempted solution: So first I have to find the joint density function which ends up being fxy(x,y) = 3/4 and then from that I would solve...
  11. DaveC426913

    Designing a Ball Joint for 135 Degree Flex in 1/4" Brass Tubing

    I am building a device out of 1/4" brass tubing. I need to join lengths in such a way as to allow the tubes to flex up to 135 degrees from straight. I haven't been able to figure out how to get that much rotation from a ball joint without the joint falling apart.See attached diagram below for...
  12. W

    Understanding Joint Density Functions: Solving for Unknown Parameters

    it seems that i can't understand the boundaries... the joint density function: f(u,v)= a , u^2 <= v <= 1 0 , else find a i just don't know how to start. any help ? thx
  13. W

    How Do You Determine the Correct Boundaries for a Marginal Density Function?

    Hi all i have problem with my h.w , i think the question is related more to math than to probability, but I'm sure someone here will find how to help me so i attached my solution with the question, i think i have difficulty to find the right boundaries of the marginal density function of...
  14. L

    Bushing Joint simulation in Ansys W14

    Is it possible to simulate a bushing joint between to parts that would also conduct heat from one part to another?
  15. F

    Finding covariance using the joint pdf

    The following question appeared on a practice exam: For f(x,y) = 24xy if 0<x+y<1 , 0<x,y 0 elsewhere find Cov(X,Y) I used Cov(X,Y) = E(XY) - E(X)E(Y) to calculate covariance, with E(XY) = \int^{1}_{0}\int^{1-y}_{0}24x^{2}y^{2}dxdy but for some reason I didn't get the...
  16. E

    Joint Distribution: U,Y - Find P(0≤X≤2/3)

    Homework Statement Let U,Y be independent random variables. Here U is uniformly distributed on (0,1) Where as Y~0.25\delta_{0} + 0.75\delta_{1}. Let X = UY. Find the Cdf and compute P(0≤X≤2/3) The Attempt at a Solution Normally a question like this is fairly straightforward but I'm having...
  17. 6

    Transformations and joint pdf's

    Homework Statement Let X1 and X2 be random variables having a joint pdf, fX1X2(x1,x2). Suppose that Y1=X1X2, and Y2=X1X2 Use the transformation result to derive an expression for the joint pdf of Y1 and Y[SUB]2 in terms of that for X1 and X2 Homework Equations The single random...
  18. S

    Calculating Limits of Integration for Joint Distributions

    http://dl.dropbox.com/u/33103477/Joint.png This is my interpretation of the limits of integration can you tell me if this is correct and also how do you calculate these limit's. Cause I'm not completely sure how they're calculated. \int_{0}^{1}\int_{1-y}^{1} ce^x e^y dx dy
  19. M

    Creating a Steel Rope Joint: Tips & Techniques

    hello friends, i am currently working on a project in which a steel rope is used to carry an object in a loop just like a chair lift. what i want to ask is what method can i adopt to make a joint of the rope that can pass through or over the pulleys and not de-track too. The rope diameter is 8...
  20. R

    How do I graph and integrate a joint PDF with multiple inequalities?

    Homework Statement Find λ given that the joint PDF of random variables X, Y, is given by: f(x,y)=\lambda x y^{2} where 0\leq x\leq y\leq 1 and 0 otherwise I have two questions: 1) How do I graph this? I'm not sure how to approach the inequality and graphing. What does this inequality...
  21. S

    Expectations of Joint Distribution.

    How would you work out E[XY] where X,Y are dependant variables in a Joint Distribution. I know there is a relationship with the conditional distributions but I can't understand the logic behind it, hence am hoping someone here can give me directions to work out this expectation.(I don't just...
  22. L

    Determining the joint probability density function

    Homework Statement A process is defined as: X(t) = Asin(ωt+\phi]) where A and \phiare random variables and ω is deterministic. A is a positive random variable. Determine the joint probability density function, PDF, of X(t) and X'(t) in terms of the joint PDF of A and\phi...
  23. B

    Robot Design: Shoulder Joint for 540N of Force

    I am making a robot that entails a moveable base and a basic moving arm. I have made a force diagram using a 50kg, 110lb weight 9the maximum intended load. Doing the math (some of it I rounded) I would need at least 540 N of force to raise the weight. How could I design a shoulder joint in such...
  24. L

    Determining joint probability density function

    Homework Statement A process X(t) is defined as X(t) = Asin(ωt + \phi) where A and \phi are random variables while ω is a deterministic parameter. Note that A is a positive random variable. Determine the joint probability density function, PDF, of X(t) and X'(t) in terms of the joint PDF of...
  25. E

    How Do You Calculate Mean and Median from a Joint Distribution Table?

    Joint Distribution (Means,Medians...) PLEASE HELP! Hi, I'm wondering if somebody could help me understand this... If you have a joint distribution with Hourly Wage (Y) Years of Education (X) 9 15 30 10 0.07 0.02 0.01 14...
  26. M

    Robotic arm revolute joint design

    I'm trying to make an elbow joint for a robotic arm that is actuated with a stepper motor and two gears. Here's a quick sketch of what I'm trying to do: http://imgur.com/mBlg7 The two bottom plates will be attached to the 'bicep' and the two upper plates will be attached to the 'forearm.'...
  27. N

    Adiabatic approximation for joint probability distribution

    Hi group, I'm a theoretical ecologist with fairly adequate training in applied math (ODE, linear algebra, applied probability, some PDEs). In my current work, I've encountered the use of adiabatic approximation to a joint probability distribution of two ever-fluctuating spatial variables. A...
  28. I

    Calculating Joint Conditional Probability with Independent Variables

    Homework Statement I have access to P(x|A) and P(y|A), P(x), P(y) and P(A), in addition to the knowledge that x and y are independent variables. I am interested in finding P(A|x,y). The Attempt at a Solution I think that P(A|x,y) = P(x,y|A) * P(A) / P(x,y) = P(x,y|A) * P(A) /...
  29. S

    How Do You Find the PDF of Z and Calculate Mean and Variance Using MGF?

    Hi guys, I'm really stuck on the following questions, not sure as to how to approach it: Let X and Y be random variables for which the joint pdf is as follows: f(x,y) = 2(x+y) for 0 <= x <= y <= 1 and 0 otherwise. Find the pdf of Z = X + Y And also: Suppose that X is a random variable for...
  30. M

    Hw in matlab about joint probability >

    Homework Statement i'd try to write the code for this question :(Discrete random variable X & Y have a joint distribution : Fx,y(x,y)=0.1u(x+4)u(y-1)+0.1u(x+3)u(y+5)+0.17u(x+1)u(y-3)+0.05u(x)u(y-1)+0.18u(x-2)u(y+2)+0.23u(x-3)u(y-4)+0.12u(x-4)u(y+3) Homework Equations I try this code in...
  31. A

    Joint probability distribution of two images

    I'm posting this here, as i feel it's more probability-related than image processing. I'm reading this lecture pdf. At end of page 1 , beginning of page 2 it says: Is this a bit vague, or am i missing something? Since we are calculating frequency of the value a in the pixels of image A, when...
  32. C

    Joint pmf of 2 binomially distributed random variables

    I hope I wrote that correctly but I'm trying to find the joint. I heard it was impossible from someone. X = A/R A~BIN(n1, p1) R~BIN(n2, p2) I know I shouldn't be using the Jacobian method for Discrete distributions but I have to do it anyway. Anyone know?
  33. W

    Joint Moment Generating Function Help

    Hi, I've no idea where to go with the question below: Joint moment generating function of X and Y - MXY(s,t) = 1/(1-2s-3t+6st) for s<1/2, t<1/3. Find P(min(X,Y) > 0.95) and P(max(X,Y) > 0.8)
  34. T

    MHB Find Average Time for Completion of Two Tasks with Joint MGF

    If the joint moment generating function of X and Y is M X,Y (t1, t2) = 6 / (1-t1) * [(1/(2-t2)) -1/(3-(t1+t2))] and X,Y are the times AT WHICH the two successive tasks are completed, find the average time for completion of the two tasks. Also find the moment generating function of the time...
  35. J

    Characteristic Function of Joint Gaussian Distribution

    This is inspired by Kardar's Statistical Physics of Particles, page 45, and uses similar notation. Homework Statement Find the characteristic function, \widetilde{p}(\overrightarrow{k}) for the joint gaussian distribution: p(\overrightarrow{x})=\frac{1}{\sqrt{(2\pi)^{N}det...
  36. S

    What is the Joint Density of C = min(A,B)?

    Homework Statement I have: f_A=\lambda e^{-\lambda a} f_B=\mu e^{-\mu b} (A and B are independent) I need to find the density of C=\min(A,B) 2. The attempt at a solution f_C(c)=f_A(c)+f_B(c)-f_A(c)F_B(c)-F_B(c)f_A(c) =\lambda e^{-\lambda c}+\mu e^{-\mu c}-\lambda e^{-\lambda c}(1-e^{-\mu...
  37. J

    MHB Finding Joint Density for Minimum of Independent Variables: $\min(A,B)$ Formula

    I have: $f_A=\lambda e^{-\lambda a}$ $f_B=\mu e^{-\mu b}$ I need to find the density for $C=\min(A,B)$ ($A$ and $B$ are independent). Is this correct or utterly wrong? $f_C(c)=f_A(c)+f_B(c)-f_A(c)F_B(c)-F_A(c)f_B(c)$ $=\lambda e^{-\lambda c}+\mu e^{-\mu c}-\lambda e^{-\lambda...
  38. R

    Joint Distribution of Complicated Variables

    Simple joint distributions such as X+Y are usually worked out in textbooks, but how would we approach a general case. For example, let X any Y be independent variables each defined on the interval [0,infinity], and having densities f(x) and f(y) respectively. How do we find, for example, the...
  39. C

    Lagrangian for two identical rods connected by frictionless joint.

    Homework Statement Hello. I have a problem with setting up the lagrangian for a system here. The problem is stated at page 8 problem 2.3 with a diagram at the following -->link<--- 2. The attempt at a solution I used two generalized coordinates corresponding to the angle between...
  40. T

    How to Determine Forces in a 2D Truss Using the Joint Method?

    Homework Statement Determine force of each member using joint method Homework Equations T = F x D The Attempt at a Solution Answers are: Fab 2465 T Fbd 1200 T Fbc 1375 C Fdc 750 C Fde 860 T (This one is what I tried) Fce 649 C Fac 1922 C Thanks.
  41. G

    Characteristic function of z (Joint?)

    I need some help. Is there a good way to do this type of question? Homework Statement Let X and Y be independent random Variables with exponential densities fX(x) = Ωe-Ωx, if X≥0 0, otherwise fY(y) = βe-βy, if y≥0 0, otherwise...
  42. I

    Programs MSE/EE joint degree or Engineering Physics?

    Right now I am a junior working towards an Engineering Physics degree and an EE minor. In addition to the physics, I've been/plan on taking a few EE and MSE classes that I have thought would be useful and interesting in the kind of work I could see myself doing. I looked over the MSE/EE joint...
  43. E

    Joint Probability Distr. of 2 Non-Independent Variables Given Marginals

    Hi, This is my first post in one of these forum; I hope someone can help me with this --thanks in advance for reading! I'm trying to find the joint probability distribution of two non-independent variables given only their marginal distributions. In fact, I'm interested in the joint...
  44. Y

    Solving Joint Convolution for P(X,Y) - 65 Characters

    I solved majority of the question I just need to find the last joint density. Found the equations at part 3. Homework Statement Show P(X-Y=z ,Y=y) = P(X) = P(|Y|) I showed P(X) = P(|Y|) Homework EquationsThe Attempt at a Solution P(X=x,Y=y) = \frac{2*(2x-y)}{\sqrt{2πT^3σ^6}} *...
  45. M

    Stats/Probability: Joint Exponential Distribution

    Homework Statement Suppose that X=time to failure for a component has an exponential distribution with lambda =.25. Suppose that 9 of the components are selected and their failure times noted. Compute the probability that 3 of the components fail between times 1 and 2, and 4 of the components...
  46. C

    Calculating the Joint PMF of Two Independent Poisson Random Variables

    X~Pois(λ)=> px(k)=e-λλk/k! Y~Pois(μ)=> py(k)=e-μμk/k! Find pX,X+Y(k,n)=P(X=k, X+Y=n) ...I know the pmf for X+Y ~ Pois(λ+μ) As I understand the joint pmf for two independent random variables would be the product of the two individual pmfs. However as X+Y is dependent on X I got really...
  47. C

    Finding the Joint PMF of Two Independent Poisson Random Variables

    Homework Statement X~Pois(λ)=> px(k)=e-λλk/k! Y~Pois(μ)=> py(k)=e-μμk/k! Find pX,X+Y(k,n)=P(X=k, X+Y=n) Homework Equations ...I know the pmf for X+Y ~ Pois(λ+μ) The Attempt at a Solution As I understand the joint pmf for two independent random variables would be the product of the two...
  48. M

    Probablity Question - Joint PDF Expectation/Variance

    Homework Statement I have been given a joint PDF for X and Y, with ranges Y>X≥0. I need to find the E(x) and E(y). Homework Equations I know E(x) = ∫(x)*(f(x,y) dx and E(y) = ∫(y)*(f(x,y)) dyThe Attempt at a Solution For ∫x*f(x,y) dx, i used the limits = x to ∞ For ∫y*f(x,y) dy, i used the...
  49. N

    Joint MBA/MA Chemistry: Advantages for Chemists

    Yes - I know this is a physics forum, but technically chemistry is a result of physics, and the chemical forums are relatively unpopulated, so I thought I'd ask you all about this as well (if it helps, replace every instance of the word 'chemistry' with 'physics')... I graduated with a B.S...
  50. H

    What is the Joint Distribution for a Bivariate Normal and Logistic Distribution?

    Hi! I would be really happy to receive some help. I have tried using Jacobians and so on, but I am stuck. I'll start with the univariate case. Let X ~ N(μ,σ) and Y = exp(X)/(1+exp(X)). What is the joint f(x,y)? According to intuition fy|x = 1, but since we are dealing with continuous...
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