Local area networks

A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building. By contrast, a wide area network (WAN) not only covers a larger geographic distance, but also generally involves leased telecommunication circuits. Ethernet and Wi-Fi are the two most common technologies in use for local area networks. Historical network technologies include ARCNET, Token Ring and AppleTalk. The increasing demand and usage of computers in universities and research labs in the late 1960s generated the need to provide high-speed interconnections between computer systems. A 1970 report from the Lawrence Radiation Laboratory detailing the growth of their "Octopus" network gave a good indication of the situation. A number of experimental and early commercial LAN technologies were developed in the 1970s. Ethernet was developed at Xerox PARC between 1973 and 1974. Cambridge Ring was developed at Cambridge University starting in 1974. ARCNET was developed by Datapoint Corporation in 1976 and announced in 1977. It had the first commercial installation in December 1977 at Chase Manhattan Bank in New York. In 1979, the Electronic voting systems for the European Parliament was the first installation of a LAN connecting hundreds (420) of microprocessor-controlled voting terminals to a polling/selecting central unit with a multidrop bus with Master/slave (technology) arbitration. The development and proliferation of personal computers using the CP/M operating system in the late 1970s, and later DOS-based systems starting in 1981, meant that many sites grew to dozens or even hundreds of computers. The initial driving force for networking was to share storage and printers, both of which were expensive at the time. There was much enthusiasm for the concept, and for several years, from about 1983 onward, computer industry pundits habitually declared the coming year to be, "The year of the LAN". In the 1980s, several token ring network implementations for LANs were developed.

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Related exercises (32)

Ellipse

A material point moves in the vertical plane Oxy such that its position vector is given by ru2004=u2004acosu2006(ωt)e_(x)u2005+u2005bsinu2006(ωt)e_(y), where a and b are positive constants such that au2004>u2004b, and e_(x) and e_(y) are the unit vectors of the axis Ox and Oy.

Show that the material point moves on an ellipse.

A material point M moves in a plane containing the fixed points A and B such that the condition ∥AM∥u2005+u2005∥MB∥u2004=u2004const is verified.

Show that the material poin

Frequency of molecular vibrations

Let us consider a hydrogen atom of mass mu2004=u20041.67u2005⋅u200510⁻²⁷u2006kg chemically bound to a metallic surface. We model the chemical bound by a spring of constant k, of natural length l₀ and of vibration frequency fu2004=u200410¹³u2006s⁻¹.

Determine the value of the spring constant k of the chemical bound, neglecting the action of the gravitational force. Frame, coordinates and system: We take the metallic surface as frame of reference and use the horizontal coordinate e_(x) oriented towar

Intersection

A missile is launched with an initial velocity v⁰ from point O. At the same time, a material point is launched with no initial velocity from point P.

Show that if the missile is initially launched along the line of fire OP, then the missile will inevitably hit the material point.

Resolution method: α is defined as the angle between the straight line OP and the horizontal and α′ is defined as the angle between the line of fire and the horizontal. Show that the intersection condition for the traject

Oscillator on an inclined plane

A material point of mass m is required to move along a line with an angle of inclination α with respect to a horizontal line. There is no friction. The point mass is attached to a spring of natural length l₀ and of constant k.

Give explicit expressions for the forces.
Determine the equation of motion.
What is the oscillation period ?

Frame, coordinates and system: We take the inclined plane as frame of reference and choose the coordinate e_(x) parallel to the inclined plane oriented towards

Excitation of a vertical harmonic oscillator

A mass m is suspended on a spring of natural length l₀ and of elastic constant k. The spring is attached to a piston. The vertical motion of the piston is described by the equation s(t)u2004=u2004s₀cosu2006(ωt)xa0.

Give explicit expressions for the external forces and determine the equation of motion.
Show that the equation of motion can be recast as, $\ddot{x}\left(t\right) + c_1\,x\left(t\right) = c_1\,s\left(t\right)\ ,$ where x(t)u2004=u2004z(t)u2005+u2005c₂ with z(t) the vertica

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