9.14 - Common Integral Forms for Reference
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Fourier Sine Transform of Piecewise Constant Function
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Today we'll discuss the Fourier Sine Transform, starting with the integral of a piecewise constant function defined on the interval from zero to a.
What does the integral represent in a physical context?
Great question! The integral helps us understand how the function behaves, like modeling a vibration in a structure. It reflects how energies are distributed.
Can we summarize the integral formula for this case?
Absolutely! It's $$ \int_0^a sin(\omega x) dx = \frac{1 - cos(\omega a)}{\omega} $$. This shows how the sine transform can describe a system over a specific interval.
What happens if we extend it beyond 'a'?
For functions extending beyond 'a', we may need to consider additional terms in the context of boundary conditions.
Can that impact the method we choose?
Yes, it certainly does! In engineering, understanding these conditions is crucial for selecting the right analytical method.
In summary, the Fourier Sine Transform helps us solve specific engineering problems effectively by focusing on interval behavior.
Fourier Cosine Transform of Exponential Decay
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Next, let's explore the integral of the exponential decay function. This has many applications in heat analysis.
What is the formula for that?
The Fourier Cosine Transform for the exponential function is given by: $$ \int_0^\infty e^{-ax} cos(\omega x) dx = \frac{a}{a^2 + \omega^2} $$. This result is particularly useful in engineering contexts.
So is this formula indicating how quickly something cools off or decays?
Exactly! It represents the behavior of processes like heat diffusion in materials over time.
Does it work for other types of equations too?
Yes, this transform can be adapted for various exponential behaviors not just cooling!
To wrap up, this integral form is crucial for modeling decay processes in engineering.
Fourier Sine Transform of Exponential Decay
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Finally, let’s look at the Fourier Sine Transform specifically for the exponential decay function.
What does this transform look like?
We have: $$ \int_0^\infty e^{-ax} sin(\omega x) dx = \frac{\omega}{a^2 + \omega^2} $$. This form is particularly applicable in systems exhibiting odd symmetry.
How does that relate to actual engineering problems?
In engineering, this could describe oscillations of systems that have certain boundary conditions and symmetrical structure behavior.
What if we need to include other responses?
We can combine these transforms to create a more comprehensive model of the system!
In closing, we see how even simple functions can be critical in engineering analysis.
Introduction & Overview
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Quick Overview
Standard
Common Fourier integral forms are provided for functions encountered frequently in engineering problems, such as sine and cosine transforms of specific functions. This highlights practical applications of Fourier integrals in addressing various engineering analyses.
Detailed
Detailed Summary
This section outlines key Fourier integral forms that are commonly used in engineering problem-solving. Specifically, it details:
- Fourier Sine Transform of a piecewise constant function defined over a bounded interval. This form is particularly useful for modeling systems with discontinuities.
- $$ \int_0^a sin(\omega x) dx = \frac{1 - cos(\omega a)}{\omega} $$
- Fourier Cosine Transform of the exponential decay function, which arises in applications involving decaying processes, such as heat conduction.
- $$ \int_0^\infty e^{-ax} cos(\omega x) dx = \frac{a}{a^2 + \omega^2} $$
- Fourier Sine Transform of the same exponential decay function, which models processes that have odd symmetry.
- $$ \int_0^\infty e^{-ax} sin(\omega x) dx = \frac{\omega}{a^2 + \omega^2} $$
These integral forms serve as reference tools for engineers to simplify and solve complex analytical problems in various fields of civil engineering, particularly in heat analysis and vibration problems.
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Fourier Sine Transform of Constant Function
Chapter 1 of 3
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Chapter Content
- Fourier Sine Transform of f(x)=1, 0
Detailed Explanation
This formula represents the Fourier sine transform of a constant function, specifically f(x) = 1, defined within the interval (0, a). The left-hand side of the equation indicates the integral of the product of the sine function sin(ωx) and the constant function over the defined interval, while the right-hand side shows the result of this transformation. Essentially, it captures how a constant function, when transformed, behaves in the frequency domain.
Examples & Analogies
Imagine you're trying to analyze how a consistent sound (like a steady note on a guitar) can be represented in terms of its frequency components. The formula gives you a mathematical way to express how that constant sound waves translate into different frequencies.
Fourier Cosine Transform of Exponential Function
Chapter 2 of 3
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Chapter Content
- Fourier Cosine Transform of e−ax:
Z ∞ a
e−axcos(ωx)dx=
a2+ω2
0
Detailed Explanation
This formula shows the Fourier cosine transform of the exponential decay function e^(-ax). Here, we see how the behavior of a decaying function over an infinite interval is transformed into a function of ω, which represents frequency. The result, a² + ω², indicates the dependency on both the exponential decay rate (a) and the frequency (ω), blending the effects of both in the frequency domain.
Examples & Analogies
Think about how a flashlight beam decreases in intensity as it moves away from the source. The equation shows how you can quantify that intensity decrease over time (the exponential decay) and then convert that information into a frequency analysis to understand the light's behavior in different contexts.
Fourier Sine Transform of Exponential Function
Chapter 3 of 3
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Chapter Content
- Fourier Sine Transform of e−ax:
Z ∞ ω
e−axsin(ωx)dx=
a2+ω2
0
Detailed Explanation
This formula represents the Fourier sine transform for the same exponential decay function e^(-ax). Similar to the previous transform, this integral takes the product of the sine function and the exponential decay over an infinite interval. The result indicates how the sinusoidal components relate to the decay rate and frequency, again yielding the result of a² + ω². This shows the dual influence of the exponential decay and the frequency in transforming the function.
Examples & Analogies
Imagine sound waves generated by a decaying source, like the fading sound of a struck bell. This equation helps you understand how the gradual fading of the sound (the exponential decay) can be analyzed in terms of its sine wave patterns across varying frequencies.
Key Concepts
-
Fourier Sine Transform: Used for modeling odd functions and vibrations.
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Fourier Cosine Transform: Applied for analyzing even functions and symmetry in engineering.
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Exponential Decay: Represents real-world processes like cooling or decay in systems over time.
Examples & Applications
Example of using the Fourier Sine Transform in analyzing beams under stress.
Using the Fourier Cosine Transform to model temperature in a cooling rod.
Memory Aids
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Rhymes
When you sine and decay with ease, Your beams and heat won't just freeze!
Stories
Imagine a concrete beam, cooling down quickly after being heated. The way the heat fades echoes the Fourier Cosine Transform, showing how things settle down smoothly.
Memory Tools
Remember Sine for Odd and Cosine for Even: S.O.C.E — Sine Odd, Cosine Even.
Acronyms
S.C.E — Sine, Cosine, Exponential
the key types of transforms in engineering scenarios.
Flash Cards
Glossary
- Fourier Sine Transform
A mathematical transformation that expresses a function in terms of the sine function, often used in analyzing odd functions.
- Fourier Cosine Transform
A transformation that represents a function using cosine functions, typically applied to even functions or heat distribution.
- Integrable
A property of a function indicating that its integral can be computed over a specified interval.
- Piecewise Constant Function
A function that has a finite number of intervals, in which it remains constant.
- Exponential Decay
A decrease that occurs at a rate proportional to the value of the variable, represented mathematically as e^-ax.
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