Software process model

•    A simplified representation of a software process, presented from a specific perspective

•    Examples of process perspectives are

*         Workflow perspective - sequence of activities

*         Data-flow perspective - information flow

*         Role/action perspective - who does what

•        Generic process models

*         Waterfall

*             Evolutionary development

*         Formal transformation Integration from reusable components

Software engineering Computer science and System engineering

Computer science is concerned with theory and fundamentals; Software engineering is concerned with the practicalities of developing and delivering useful software Computer science theories are currently insufficient to act as a complete underpinning for software engineering. System engineering is concerned with all aspects of computer-based systems development including hardware, software and process engineering. Software engineering is part of this process System engineers are involved in system specification, architectural design, integration and deployment.

  

TYPE I and TYPE II SUPER CONDUCTORS

        Superconductors are differentiated by there magnetization curves by two types. They are TYPE I and TYPE II Super conductor.

In Pure Material or TYPE I Superconductor, the specimen cannot resist the magnetic field from critical applied field H_C. After H_C magnetic field penetrate the specimen totally. It losses its super conducting properties completely.

In TYPE II superconductor usually alloys or composite, when the applied field crosses H_C1 the specimen starts to loss its super conductivity. But field cannot penetrate fully and super conducting property is retained in the part of the specimen up to H_C2. This region is called vortex state. After H_C2 the specimen is in normal state.

APPLICATIONS:-

1. Flux trapping.
2. Flux shielding.
3. Flux concentration.
4. Magnetic bearings.
5. Electric power transmission.
6. SQUID Superconducting Quantum Interference Device.
7. MRI Magnetic Resonance Imaging.
8. MAGLEV MAGnetic LEVitation.

Meissner Effect

           Transition temperature is the temperature at which the resistance of the material fell sharply to zero or close to zero. Superconductor would have no resistance at all.

When temperature is lowered below T_C, the magnetic lines of force are expelled from the specimen. This is called Meissner effect.

SUPERCONDUCTOR

         At very low temperature most of the metals and alloys allows the current to pass through it freely without resistance. This phenomenon is called Superconductivity.

            It was discovered in 1911 by Kammerlingli Onnes. He was experimenting with mercury sample at low temperature and studies the resistance of mercury. The Resistivity of the mercury was decreasing normally when the temperature was decreases. But at a particular temperature T_C = 4.15 K the resistivity suddenly dropped to zero. This property is called Superconductivity. The superconducting sate the conductional electrons in the metal forms a loosed pair that persistence the electric current.

            Superconducting property occurs in many metals, alloys, metalloids and doped semiconductors. Some material became super conducting only under high pressure. Eg. Silicon T_C = 8.3 K; pressure = 165 kilo bar. Even trace quantities of foreign bodies if magnetic can lower the transition temperature very much. Decay time of the superconductor is not less than 100,000 year.