Models Definition and 369 Threads

In models of exponential growth, we have an intrinsic growth rate (r) that is calculated as the difference of birth rates to death rates. With the logistic growth model, we also have an intrinsic growth rate (r). How then do birth rates and death rates relate to the intrinsic growth rate in...

I have some very simple questions. 1. What are the real life applications of the biological neuron models (for example Hodgkin-Huxely model)? 2. Is their any online database from where I can get the original recordings data of a neuron? 3. or is there any way that I can...

I have a rainfall (mm) vs. year plot of a catch basin (see Excel file below) and I would like to get it's frequency curve. But before that, I need to fit certain distribution models (i.e. log-Pearson Type III and Gumbel Distributions) to my plot to be able to know the fittest model that I can...

Homework Statement Design a π section symmetrical attenuator to provide a voltage attenuation of 15 dB and a characteristic impedance of 600 Ω. Zc=600Ω,\alpha=15dB (attenuation) Z1,Z3=? Homework EquationsThe Attempt at a Solution \alpha[dB]=20log(Vin/Vout)=15 \alpha=5.623...

Hi, I think I read here; maybe not, that , within a non-standard model of the Reals, it is possible to have probabilities , say over an interval, so that each point has non-zero probability. AFAIK, the transfer principle ( a.k.a elementary equivalence of models) does not disallow having a...

Homework Statement Construct and test the ∏ section symmetrical attenuator. Measure and record the Input & Output Voltages of the attenuator and determine the attenuation in dB. Homework Equations Vout = Vin * [ R2 / (R1 + R2) ] Decibel Attenuation (dB) = 20LOG10(Vout / vin)...

[/SUB]Homework Statement Design a ∏ section symmetrical attenuator to provide a voltage attenuation of 15 dB and a characteristic impedance of 600 Ω. Homework Equations ZS = ZL = Z R1 = R3 = Z (K + 1 / K -1) R2 = Z (K2 - 1 / 2 K) The Attempt at a Solution Z = 600Ω K =...

Homework Statement Define a Hidden Markov Model with the following parameters: State space S={1,2,3}, alphabet A = {a,b,c,}, P = 0 .5 .5 1 0 0 0 1 0 initial probability vector, ∏ = 1 0 0...

Hello, In my Differential Equations class we are learning about modelling with first order differential equations. We learned that Newton's Law of Cooling breaks down when the temperature of the object is approaching the temperature of the room its in. You eventually get to a point where you...

Homework Statement Through donations the food bank tries to feed as many people as possible. Assume there are no backorders - any unsatisfied demand is lost. The food bank also has limited facilities to store donations, 200,000lbs maximum can be held in storage. Assume donations are processed...

I see there are mainly discussed here very abstract approaches like string theory. I would like to suggest a general discussion about much less abstract models: to get not exactly beyond, but rather behind the standard model - ask about the internal structure of particles (behind abstract...

Homework Statement Suppose that the velocity v(t) (in m/s) of a sky diver falling near the Earth's surface is given by the following exponential function, where time is measured in seconds. v(t) = 55 (1-e-0.18(t)) Find the initial velocity of the sky diver and the velocity after 6...

Here is my previous post! please look at pages 3 - 4 to see what I am talking about. http://mathhelpboards.com/pre-algebra-algebra-2/mathematical-modeling-6006-4.html I figured out how to input the quadratic and logarithmic equations into wolfram, this is what i got. Let me know if its correct...

Hello, I am quiet new to this subject. I am reading over grand unified theory and found that there are quiet a number of Symmetries, like U(1) and SU(2)..... Can anybody help me in finding all the types of symmetries and how it evolved and what are they basically are? Thanks

according inflation, the universe should to be uniform in all directions at large scale, but observations from the Planck spacecraft found fluctuations in the cosmic microwave background that undermines the model. http://www.kavlifoundation.org/science-spotlights/kicc-planck-universe

I was reminded of this point by a recent discussion in the "Classification of manifolds ..." thread. The question is this: As I understand it, the NCG framework requires a Riemannian manifold. Given this, at best one could hope to obtain a Euclidean theory, right? So is it fair to say...

Unlike other symmetries (like electroweak symmetry), SUSY is spontaneously broken at any non-zero temperature due to some variation of the fact that the boundary conditions on bosons and fermions in thermal QFT are different. If this is the case, what is the rationale for considering SUSY...

In QED, Feynman says: "The situation today is, we haven't got a good model to explain partial reflection by two surfaces; we just calculate..." I've been frustrated in that I'm still not clear if this is the case (is there still no model to explain the behavior). A similar dynamic seems to...

Hello all! I actually have a few doubts regarding "gauss law" when applied "for different models of sphere" First, If we place a charge 'Q' inside a spherical shell at the center (somehow) then it should come out to its surface that means in no way can we do it. True or False? Next...

This is a question out of model theory. (This preamble is due to the fact that "model" and "theory" are used in different ways in different fields.) Is there any specific relationship between two theories which have the same models? A knee-jerk reaction would be to say that they are isomorphic...

From time to time I try to get an overview regarding the current status of LQG. Unfortunately there seem to be a lot of interesting ideas and new proposals, but I am missing a summary paper which addresses and summarizes both main achievements and main open issues. What about status of...

Hi, I am a first year stats grad student and I am taking a class on linear models. The book and lectures focus on the format of definition, proof, lemma, definition, proof, lemma etc. However, I cannot seem to find anywhere some practice problems where I could use these definitions before I...

Right, Hello, I am new to this, and do not have much understanding, but can someone here help explain the Dimension Models and String theory to me?

Homework Statement Given that a population, P, after t months, can be modeled by the logistic model dP/dt = .3 P (3.5 - P/40). P(0) = 30 a) Solve the diff eq b) Find the population after 2.5 months c) Find lim P(t) as t -> infinity Homework Equations P(t) = P0 P1 /(P0 + (P1...

Here is an exercise from Shawn Hedman's course of logic, like all others I have posted. I would say that only the empty graph is the correct solution, because if a structure is not empty then I can derive $\exists xR(x,x)$ from each of the given sentences.

Hi everyone, So I have a set of relaxation data and creep data for a solid polymer that I want to analyse. In the relaxation I use the Prony series derived from the generalized maxwell equation (incl a spring) and get a very nice fit. My question is if I should use the same to model the...

This is the same mathematician who did that paper on the zombie apocalypse a couple years ago: pdf here http://mysite.science.uottawa.ca/rsmith43/bieber.htm

The academics and the technicians of a university faculty are planning a paintball battle and the mathematicians are trying to predict their chances of winning with a continuous model. They are representing the numbers in the two teams at any time t as and respectively and have decided that the...

Hello guys, I need to understand the ARCH and GARCH models and so I need some advice on where I should begin my study. In order to understand ARCH models, am I right to begin with studying autoregression? If so can you guys provide me with a link or book I should look into... By the way, I...

Hi, I try to teach myself Hidden Markov Models. I am using this text "www.cs.sjsu.edu/~stamp/RUA/HMM.pdf" as Material. The Introduction with the example was reasonable but now I have trouble in unterstanding some of the derivation. I can follow the math and use the formulas to get...

I have had this question for a long time and thought this forum might be the best place to answer.. If there is an infinite number of bangs happened before the big bang, our universe's bang should never have happened because it would require an endless number of bangs that -by definition- would...

So far in my physics education I've developed a basic understanding of two nuclear models, the liquid-drop model and the shell model. I read something a while ago (don't have the text on hand to quote the exact phrasing, unfortunately) that seemed to imply, in a couple of places, at least...

Hi, I appreciate the basics if static models, but I'm wondering just how static they are. I understand there is no expansion, but is there any element of evolution? (For example, colliding galaxies, collapsing dust clouds, etc.) Regards, Noel.

Homework Statement I have a couple of notation interpretation questions: 1) What does f_X(x|θ) represent in this case? The realization function of of our random vector X for some value x and a parameter θ (so that if our random vector has n random variables, its realization vector will be a...

Are "flowing space" models compatible with GR? Recently papers have been published with new "flowing space" models for GR. In particular a "flowing river" model by Hamilton: http://ajp.aapt.org/resource/1/ajpias/v76/i6/p519_s1? http://arxiv.org/abs/gr-qc/0411060 "In this model, space flows...

What is meant by "Early atomic models predicted...noble gas...stable" Hello, I am troubled by the following statement "Early models of atomic structure predicted that atoms and ions with noble gas electron arrangements should be stable" Is this referring to the Niels Bohr model or am I...

As an understanding exercise in my general relativity course my professor recommended proving to ourselves that all Robertson-Walker models are conformally flat. However, I am unsure of how to approach such a proof. Thanks in advance for any help.

Spice Models -- LM5111 & LM5112 Hello Everyone, I am looking Spice model for the MOSFET Gate Drivers (LM5111 & LM5112). If anyone have this models please forward to me.

If we were to assume that in a Robertson-Walker model that the cosmological constant was less than zero, would this imply that at a finite time in the future the universe would undergo a "big crunch"? More importantly, would this imply the scale factor a(t) is equal to zero at that time?

Homework Statement I will use an example to showcase my confusion: Suppose a person watches show A 2/3 of the time, show B 1/2 of the time, and both show A and show B 1/3 of the time. For a randomly selected day, what is the probability that the person watches only show A? For a randomly...

The normalized wave function for a particle in a 1D box in which the potential energy is zero between x= 0 and x= L and infinite anywhere else is normalized wave function = sqrt(2/L)*sin(npix/L) What is the probability that the particle will be found between x= L/4 and x= L/2 if the...

hey everyone... i am working on an assignment of cosmological models and beginning and ending of the universe but unable to find something that is compact and describe it all.. can anyone help me in making of this assignment please

For a general family of dynamic models, xk+1=f(xk), oscillation can occur; for example, the function xk+1=xn2-1 experiences oscillation under the starting value 0: (x2=x12-1=x2=02-1→x2=-1→x3=x22-1=x3=-12-1→x3=0) This type of oscillation must be capable of detection before actually pluggin...

Say we have 2 models: ln(y) = \beta_0 + \beta_1 x_1 + \cdots + \beta_nx_n with a known R^2 and y = \beta_0 + \beta_1 x_1 + \cdots + \beta_nx_n with a known R^2 Now I know that we can not compare the R^2's from these 2 models to determine goodness-of-fit and I am also aware of how we can...

Does anybody know what is the status of supersymmetric inflation model after latest results of LHC concerning SUSY? Have some models been excluded? or do you know some review papers talk about that issue?

Hi As I understand it there are several attmepts to explain the low entropy configuration of the universe at the big bang. Is seems to me the choices on the table that I am aware of are a mutliverse as in the Caroll/Chen model . A cyclic universe as in the CCC model or some hybrid of the two...

where can i get Solidworks models of spur gears? I have Solidworks student edition, and it doesn't include the toolbox that you can use to create gears. thanks

An interesting and well presented new paper by Kumar and Xu: "Observational constraints on a cosmological model with variable equation of state parameters for matter and dark energy" http://arxiv.org/abs/1207.5582 The idea of a variable equation of state for matter and dark energy is not...

Dear All, Appreciate if you can guide me on understanding the ultimate pressure of vacuum pump. I have two models for review. One has ultimate pressure of 1 x 10^-4Torr the other has 2 x 10^-3Torr. From this can it be said that the vacuum capability of the first pump (1 x 10^-4)...

I have been acquiring some nice molecular models of graphene, buckyballs, and things like the model below. http://www.indigo.com/images/product/172.jpg One thing I have not been able to find are crystal models with the different orientations like face-centered cubic, body-centered cubic...