


Title

Cardiovascular Fluid Mechanics





Abstract 
This collection contains resources that are useful for the physicist to get a quick introduction to the physics of the cardiovascular system. This includes the mechanical aspects of the heart as a pump, the electrical and chemical regulation methods, chemical engineering aspects of drugs, physical aspects of interventions and diagnostic tools etc. 


Title

Infinite loop in a software program





Abstract 
An infinite loop (also known as an endless loop or unproductive loop) is a sequence of instructions in a computer program which loops endlessly, either due to the loop having no terminating condition, having one that can never be met, or one that causes the loop to start over. In older operating systems with cooperative multitasking, infinite loops normally caused the entire system to become unresponsive. With the nowprevalent preemptive multitasking model, infinite loops usually cause the program to consume all available processor time, but can usually be terminated by the user. Busywait loops are also sometimes called "infinite loops". One possible cause of a computer "freezing" is an infinite loop; others include deadlock and access violations. 


Title

Overdamped and Critically Damped Oscillations





Abstract 
The value of the damping ratio ζ determines the behavior of the system. A damped harmonic oscillator can be:
(a) Overdamped (ζ > 1): The system returns (exponentially decays) to equilibrium without oscillating. Larger values of the damping ratio ζ return to equilibrium more slowly. (b) Critically damped (ζ = 1): The system returns to equilibrium as quickly as possible without oscillating. This is often desired for the damping of systems such as doors. (c) Underdamped (0 < ζ < 1): The system oscillates (at reduced frequency compared to the undamped case) with the amplitude gradually decreasing to zero. (d) Undamped (ζ = 0): The system oscillates at its natural resonant frequency (ωo).
Source: Wikipedia 


Title

RLC Circuit Oscillations





Abstract 
An RLC circuit (or LCR circuit) is an electrical circuit consisting of a resistor, an inductor, and a capacitor, connected in series or in parallel. The RLC part of the name is due to those letters being the usual electrical symbols for resistance, inductance and capacitance respectively. The circuit forms a harmonic oscillator for current and will resonate in a similar way as an LC circuit will. The main difference that the presence of the resistor makes is that any oscillation induced in the circuit will die away over time if it is not kept going by a source. This effect of the resistor is called damping. The presence of the resistance also reduces the peak resonant frequency somewhat. Some resistance is unavoidable in real circuits, even if a resistor is not specifically included as a component. A pure LC circuit is an ideal which really only exists in theory.
Source: Wikipedia 


Title

Damped Oscillations





Abstract 
In physics, damping is an effect that reduces the amplitude of oscillations in an oscillatory system, particularly the harmonic oscillator. This effect is linearly related to the velocity of the oscillations. This restriction leads to a linear differential equation of motion, and a simple analytic solution. In mechanics, damping may be realized using a dashpot. This device uses the viscous drag of a fluid, such as oil, to provide a resistance that is related linearly to velocity. Source : Wikipedia 


Title

Beats





Abstract 
In acoustics, a beat is an interference between two sounds of slightly different frequencies, perceived as periodic variations in volume whose rate is the difference between the two frequencies.
With tuning instruments that can produce sustained tones, beats can readily be recognized. Tuning two tones to a unison will present a peculiar effect: when the two tones are close in pitch but not yet identical, the difference in frequency generates the beating. The volume varies like in a tremolo as the sounds alternately interfere constructively and destructively. When the two tones gradually approach unison, the beating slows down and disappears.
Source : Wikipedia 


Title

Pendulum oscillation





Abstract 
A pendulum is a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced sideways from its resting equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the equilibrium position. When released, the restoring force combined with the pendulum's mass causes it to oscillate about the equilibrium position, swinging back and forth. The time for one complete cycle, a left swing and a right swing, is called the period. A pendulum swings with a specific period which depends (mainly) on its length.
Source : Wikipedia 


Title

Rijke Tube





Abstract 
Rijke's tube turns heat into sound, by creating a selfamplifying standing wave. It is an entertaining phenomenon in acoustics and is an excellent example of resonance. P. L. Rijke was a professor of physics at the Leiden University in the Netherlands when, in 1859, he discovered a way of using heat to sustain a sound in a cylindrical tube open at both ends. He used a glass tube, about 0.8 m long and 3.5 cm in diameter. Inside it, about 20 cm from one end, he placed a disc of wire gauze as shown in the figure at right. Friction with the walls of the tube is sufficient to keep the gauze in position. With the tube vertical and the gauze in the lower half, he heated the gauze with a flame until it was glowing red hot. Upon removing the flame, he obtained a loud sound from the tube which lasted until the gauze cooled down (about 10 s). It is safer in modern reproductions of this experiment to use a Pyrex tube or, better still, one made of metal.
Source : Wikipedia 


Title

Complex Numbers





Abstract 
A complex number is a number which can be put in the form a + bi, where a and b are real numbers and i is called the imaginary unit, where i2 = −1. In this expression, a is called the real part and b the imaginary part of the complex number. Complex numbers extend the idea of the onedimensional number line to the twodimensional complex plane by using the horizontal axis for the real part and the vertical axis for the imaginary part. The complex number a+bi can be identified with the point (a, b). A complex number whose real part is zero is said to be purely imaginary, whereas a complex number whose imaginary part is zero is a real number. In this way the complex numbers contain the ordinary real numbers while extending them in order to solve problems that cannot be solved with only real numbers. Complex numbers are used in many scientific fields, including engineering, electromagnetism, quantum physics, and applied mathematics, such as chaos theory. Italian mathematician Gerolamo Cardano is the first known to have introduced complex numbers. He called them \"fictitious\", during his attempts to find solutions to cubic equations in the 16th century. (Source: Wikipedia) 


Title

Spring mass oscillation





Abstract 
In classical mechanics, a harmonic oscillator is a system that, when displaced from its equilibrium position, experiences a restoring force, F, proportional to the displacement, x. When a spring is stretched or compressed by a mass, the spring develops a restoring force. Hooke's law gives the relationship of the force exerted by the spring when the spring is compressed or stretched a certain length. 

