Recent content by ENgez

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    I Textbook gives the gradient of a scalar as a scalar

    Thanks, I believe I have found the cause of my confusion. The model problem is 1-dimensional (x is the only free parameter). This makes the gradient a scalar in the sense that it is a magnitude that can either be positive or negative. This also makes the divergence and the gradient basically...
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    I Textbook gives the gradient of a scalar as a scalar

    Background: I am currently reading up on homogenization theory. I have a simple conductivity model (image attached). u is a scalar function (such as potential or temperature). The textbook proceeds by giving a series expansion for the gradient of u (image attached). the problem is that the...
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    Bounding p-norm expression using p-norm inequality

    problem statement: need to show: ||w||_p^2+||u||_p^2-2(||u||_p^p)^{\frac{2}{p}-1}\Sigma_i(u(i)^{p-1}w(i)) can be bounded as a function of ||w-u||_p^2 where p\in[2,\infty) work done: the expressions are equal for p=2, and i suspect that...
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    I First order logic - help with translation algorithm between

    given a dictionary \Sigma = \left \{f(),g(),R(,),c_0,c_1,c_2 \right \} and a sentence \phi over \Sigma, I need to find an algorithm to translate \phi to \psi over \Sigma' where \Sigma' = \left \{Q(,,,), = \right \} (Q is a 4-place relation symbol), so that \psi is valid iff \phi is valid. I...
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    Number of ways to arrange n numbers in k groups

    tnx for the reply, but the groups are distinct, as I am interested in the number of ways to shuffle them around. you can assume that n/k is an integer.
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    Number of ways to arrange n numbers in k groups

    my mistake, every k/n is supposed to be n/k.
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    Number of ways to arrange n numbers in k groups

    Hello, I was given a question (not a HW question..) in which i was asked to calculate the number of ways to sort n numbers into k groups, where for any two groups, the elements of one group are all smaller or larger than the elements of the other group. The answer is supposed to be...
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    Selecting Low cost, High heat-resistant plastics

    Well, not necessarily I just assumed the material would be a plastic. Any suggestions?
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    Selecting Low cost, High heat-resistant plastics

    Hello, For a current project, I am searching for high operating temperature (200C-300C), Medium Strength (~80 Mpa UTS) and low cost plastics (or at least not extremely expensive). So far the closest I found is nylon 6/6 reinforced with 30% carbon fiber. I also found something called Vespal...
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    Aerodynamic coefficients of non slender cylindrical body

    hello, I am trying to calculate the location of the center of pressure for a non slender cylinder with a cone shapes nose. Referencing the internet and notes from a aerodynamics course, all the methods are for slender bodies. unfortunately, my body is not slender. I am reluctant to go to CFD...
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    Using a bimetallic coil to turn a pulley

    Thank you for the reply. I am aware that bimetallic coils are used to drive the needle in a thermometer. What I am asking is if this concept can be used to do heavier work, like spin a pulley (wheel), and If there are examples of such mechanisms.
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    Using a bimetallic coil to turn a pulley

    I attached an illustration to further clarify. Will this work? If so, How can i calculate the angle of revolution as a function of temperature gradient?
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    Using a bimetallic coil to turn a pulley

    Hello, I am looking at the possibility of turning a pulley using a bimetallic coil embedded inside. How can I calculate the thermal "spring constant" of the coil, as a function of geometry and material properties? Does anyone know of devices with similar actuation mechanisms? thank you.
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    Difference in strength between extrusions and sheet metal

    Yes, it is common knowledge among some of the more experienced engineers, although there is no concrete theory to back it up. I am just fact checking. I understand that identical cross sections should have the same stiffness, but allegedly, the fabrication process itself (bending or extrusion)...
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