Part 2 Mutual Attraction

Medieval astronomy was dominated by the writings of Aristotle.  Aristotle divided motion into earthly lines and heavenly circles, so the planets must surely move about us in perfect circles.  Astronomers soon learned this wasn’t true, but the physics of Aristotle was so deeply rooted in the minds of scholars that astronomers imposed circular motion upon the heavens for a thousand...

Categories:

Our great cosmic motion

Image credit: Armando Bernui, Braz. J. Phys. vol.35 no.4b, 2006 ...

Categories:

Beyond Baryons

Image credit: Frank Close, Nature 424, 376-377(24 July 2003). “In any case, the number three fitted perfectly the way quarks occur in nature.” -Murray Gell-Mann ...

Categories:

Weekend Diversion

 Chess is Almost Solved  Image credit: © 2013 Masterpiecegift.com. “There are some things we do much better than computers, but since most of chess is tactically based they do many things better than humans. And this imbalance remains. I no longer have any issues. It’s a bit like asking an astronomer, does he mind that a...

Categories:

For the love of science

  Image credit: NASA / ESA. “When I say, ‘I love you,’ it’s not because I want you or because I can’t have you. It has nothing to do with me. I love what you are, what you do, how you try. I’ve seen your kindness...

Categories:

Why did the Universe start off with

Hydrogen, Helium, and not much else   Image credit: Frank X. Timmes of http://cococubed.asu.edu/. “I see a lot of new faces. But, you know the old saying, ‘out with the old, in with the nucleus.’”...

Categories:

Main Sequence Stars

Credit: NASA The Sun The majority of stars in the galaxy, including our Sun, Sirius and Alpha Centauri A and B are all main sequence stars. The Sun's relative longevity and stability have provided the conditions necessary for life to evolve here on Earth. Our understanding of the processes involved and characteristics of this key group of stars has progressed in parallel with our...

Categories:

That’s So Random

Imagine you were standing in the center of a circle 100 meters in radius.  How long do you think it would take to leave the circle?  Usain Bolt could do it in 10 seconds, but most people could leave the circle in under a minute.  After all, it’s just a casual 100 meter stroll and you are out of the circle.  But suppose we...

Categories:

Massive evidence

The center of our galaxy is about 27,000 light years away in the direction of the constellation Sagittarius.  That isn't a large distance on astronomical scales, but it is hidden by gas and dust so we can't observe it in visible light.  We can, however, observe it at infrared and radio wavelengths,...

Categories:

Part 1 A Muse of Fire

In the mid-1800s, astronomy faced a serious problem.  No one knew how the stars shone.  Now a little mystery never hurt anyone, but in this case it was deeply perplexing.  By this time we had a solid understanding of energy, and that energy is conserved.  That is, energy must come from somewhere, and it...

Categories:

Proven World

In Medieval Europe, the physical universe could be divided into two parts: the Earth and earthly events (chaotic and temporary) and the heavens (structured and eternal).  That's a bit of an over simplification, but the idea was that the Earth and heavens were governed by different rules.  In the heavens the stars were fixed and eternal.  The motion of the planets were thought to move in...

Categories:

The Way the Universe Changed

At the end of the 1800s we finally knew how the universe worked.  Newton’s laws of motion and gravity had been studied for 200 years, and had become the pinnacle of scientific precision.  James Clerk Maxwell had unified the electricity, magnetism and light into a single elegant theory, and...

Categories:

A bit about the Atari freak

Stats Name: Yiannis AKA: Alias "X" Age: 35 Profile: Hacker (which, unlike Cracking, does not involve computer security in any way) Location: Canberra, Australia ...

Categories:

Robugs 3D

Introduction Robugs are 'robotic bugs' whose behaviour is controlled by user-designed circuits. It will be an educational tool as much a game, and provide a more complex/richer simulation than other similar programs. The project is being written in Java (JDK 1.5/Java3D 1.3)....

Categories:

A java logo & link would go here if Sun permitted it

Palaver is a multi-platform IRC client, supporting a pluggable architecture. Other IRC clients support 'scripting' in an attempt to let users customise their client. The problem with scripting is that it cannot change the basic appearance of the client, or add...

Categories:

A java logo & link would go here if Sun permitted it

Palaver is a multi-platform IRC client, supporting a pluggable architecture. Other IRC clients support 'scripting' in an attempt to let users customise their client. The problem with scripting is that it cannot...

Categories:

CS_Limestone, a map for Counter-Strike

CS_Limestone, a map for Counter-Strike You probably won't ever come across this map while playing online, as it has fairly high r_speeds. It works great during LAN sessions though, where everyone has decent PCs...

Categories:

A java logo & link would go here if Sun permitted it

Palaver is a multi-platform IRC client, supporting a pluggable architecture. Other IRC clients support 'scripting' in an attempt to let users customise their client. The problem with scripting is that it cannot change the basic appearance of the client, or add...

Categories:

Overview of Sanity4J

Sanity4J is primarily a tool for running multiple Java code static analysis tools. Static Analysis tools are used to provide pointers to possible issues in code during the development cycle, as an automated form of code-review. Use of these tools helps to improve the quality of code and reduce the amount of software defects that are delivered for system testin...

Categories:

A Semester of First Year Physics

Lecture 14 (RC, RL and RLC AC circuits) In this lecture complex numbers are used to analyse A.C. series circuits, in particular: • Resistance Capacitance (RC) circuits • Resistance (Pure) Inductance (RL) circuits • Resistance (Pure) Inductance and Capacitance (RLC) circuits • Resistance (Real) Inductance and Capacitance (RLC) circuit...

Categories:

RC, RL and RLC Circuits

Lab RC, RL and RLC Circuits Course 126/151 ...

Categories:

CIRCUITS RC RL et RLC EN REGIME TRANSITOIRE

  1 INTRODUCTION  L'étude des régimes transitoires dans les circuits RC RL et RLC doit désormais faire intervenir l'acquisition de données. L'oscilloscope numérique actuel dont le convertisseur analogique numérique 8 bits n’est pas assez performant. Il sera utilisé en mode analogique comme instrument de contrôle indispensable pour bien préparer l’acquisition des mesures avec l’interface Orphy GTI . Le traitement informatique des données, la...

Categories:

RL, RC, and RLC Circuits

The primary goal of this assignment is to quickly review what you already know about capacitors, inductors, and AC circuits and to extend your new circuit analysis skills to cover sinusoidal signals. The assignment draws from Chapters 6-10 of your text. You will also learn how to use Spice to...

Categories:

LES GRADATEURS

Introduction : Un gradateur est un convertisseur alternatif / alternatif permettant, à partir d’une source alternative de valeur efficace fixe, d’obtenir une tension alternative à valeur efficace réglable. Les composants utilisés sont généralement les thyristors et les triacs....

Categories:

LES HACHEURS

Introduction : Les hacheurs sont des convertisseurs continu /continu permettant de construire une source de tension continue variable à partir d’une source de tension continu fi...

Categories:

Exercice 1

Un hacheur alimente depuis une source de tension constante Ua une machine à courant continu à aimants permanents. Les interrupteurssupposés parfaits commutent à une fréquence fixe 1/T de 20kHz. Les couples d’interrupteurs(K1 K3) et (K2 K4) sont commandés de façon complémentaire avec un rapport cyclique α. ...

Categories:

Support graphique pour exercice 2

EXERCICES SUR L’ELECTRONIQUE DE PUISSANCE, SUR LA TRANSFORMEE DE LAPLACE, SUR LES VARIATEURS DE VITESSEET SUR LES ASSERVISSEMENTS...

Categories:

2 exercices corrigés d’Electronique de puissance sur l’onduleur

Exercice Ond01 : onduleur autonome  On réalise le montage suivant en utilisant quatre interrupteurs électroniques, fonctionnant deux par deux ...

Categories:

4 exercices corrigés d’Electronique de puissance

sur le hacheur Exercice Hach01 : hacheur série On alimente un moteur à courant continu dont le schéma équivalent est donné ci-dessous, à l'aide d'un hacheur. L'interrupteur électronique K et la diode sont supposés parfaits. La période de hachage est T, le rapport cyclique α....

Categories:

Exercices Hacheur

Exercice n°1 : Un hacheur série alimente un moteur à courant continu. On utilise un oscilloscope bi courbes dont les deux voies sont branchées comme indiqué sur le schéma ci-dessous. La résistance r a pour valeur 1...

Categories:

Ch1 : Composants pour l’électronique de puissance page

CHAPITRE 1 :COMPOSANTS POUR L’ELECTRONIQUE DE PUISSANCEIntroduction : On s’intéressera à la mise en évidence des caractéristiques des composants à semi conducteurs utilisés dans les systèmes électroniques de puissance. On identifiera leurs principales caractéristiques et les conventions simplificatrices permettant l’analyse des montages fondamentaux : Redresseurs, Hacheurs, Gradateurs et Onduleurs.Ces montages constituent ce que l’on appelle les convertisseurs statiques. Ce sont des systèmes électroniques permettant le transfert de l’énergie...

Categories:

2.Commande électronique des moteurs

2.1     Introduction La commande de vitesse des moteurs constitue l’application la plus importante de l’électronique de puisssance.  Les installations industrielles utilisent de plus en plus des variateurs électroniques de vitesse à thyristors, soit pour obtenir la vitesse d’entraînement optimale de machines pour...

Categories:

Cours 15M Electronique de puissance Résumé de théorie

TECCART INTERNATIONAL 2000 inc.  3155, rue. Hochelaga, Montréal, Québec (Canada) H1W 1G4   RÉDACTION Michel Puche DESSINS ET CONCEPTION GRAPHIQUE Michel Puche RÉVISION TECHNIQUE Pierre Asselin RÉVISION LINGUISTIQUE François Gaudreau COMMISSION DE VALIDATION Formateurs de l’OFPPT...

Categories:

Plan Comptable Marocain

                                                               61712 Primes et gratifications                                                                61713...

Categories:

Les outils de base de l’algorithmique

 AlgorithmiqueExercice 1 :Ecrire un algorithme qui demande les coordonnées de deux points dans le plan, calcule et affiche à l’écran la distance entre ces deux point...

Categories:

Les outils de base de l’algorithmique

Algorithmique Exercice 1 : Ecrire un algorithme qui demande les coordonnées de deux points dans le plan, calcule et affiche à l’écran la distance entre ces deux points. N.B.   la distance entre deux points A(x1,y1) et  B(x2,y2)    est :    AB= sqrt((x2-x1)^2  + (y2-y1)^2)  on donne la fonction sqrt(x) qui renvoie la racine carrée d’un nombre réel  x ....

Categories:

La surcharge des opérateurs en langage C++

 Langage C++Exercice 1 :Définir une classe permettant d’additionner, de soustraire, de multiplier, de diviser et de donner l’opposé (-) des fractions (rationnels comprenant numérateur et dénominateur) en utilisant la surcharge de ces opérateurs.Créer un programme permettant de tester cette classe.            ...

Categories:

Langage C++  La surcharge des opérateurs en langage C++ Exercice 1 : Définir une classe permettant d’additionner, de soustraire, de multiplier, de diviser et de donner l’opposé (-) des fractions (rationnels comprenant numérateur et dénominateur) en utilisant la surcharge de ces opérateurs. Créer un programme permettant de tester cette classe.               Solution : #include <iostream.h> class operation{ float num; float deno; public: operation(float...

Categories: