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RESISTANCE AND CONDUCTANCE SUPERCONDUCTIVITY
Hydrofracturation (Figure) allow to measure directly both the orientation of the horizontal components od stress (SH et Sh) and the magnitude of this stress (SH - Sh). This technique is based on the rock fracture in presence of fluids using a fluid pressure larger than the lithostatic pressure.
Figure 6.8. The hydrofracturation technique. A section of the borehole is isolated in-between inflating packers, and a liquid is injected in the isolated portion up to fracture (Pfract). After fracturation, pressure decreases and stabilizes at a Pic value.
Can you represent the different stages of hydrofracturation in a Mohr diagram ?
These techniques give a measurement of the local state of stress. However the local state of stress is perturbated by the borehole itself, or by the pressure induced by the packers. In certains cases, the measured stress values can be corrected, for example by modeling the stress trajectories aroung the borehole.
The fractures are viewed, either directly via their print-marks onto packers placed alon the borehole, or indirectly by imaging them (Figure).
Figure. Printmarks (recorded on a packer) of the microfractures resulting from hydrofrac-turation, and observed after extraction from the borehole.
Figure ; Images obtained through tele-cameras introduced in a borehole (1050 deep) before (left-hand side) and after (righ-hand side) hydraulic fracturation. In-between the white arrows, the imaged fracture has a ESE azimuth.
This technique is the most precise for the determination of the orientations and magnitudes of Sh and SH.
----------- Exercice : Traduire cette légende et expliquer la succession des 3 figures suivantes qui illustrent comment la contrainte se concentre autour dun trou de forage.
RESISTANCE AND CONDUCTANCE SUPERCONDUCTIVITY
Subtechnical vocabulary
load (noun) the supply of electricity to a particular place The external energy source includes the wires, loads, switches, etc. galvanic cell a cell by zinc producing electricity A galvanic cell is an elementary electric circuit. incandescent (adjective) giving a bright light when heated An incandescent lamp is a device in which we can observe some forms of energy. internal ( adjective) inside something Internal combustion engine produces power by burning petrol. external(adjective) outside surface of something Electric circuit is divided into internal and external circuits. vessel (noun) a tube that carries liquid Two vessels are filled with liquid. rheostat ( noun) a piece of equipment that controls the loudness of a radio or the brightness of an electric light. Electric circuit consists of a 2-V battery, rheostat, a voltmeter, etc. drop ( verb) to fall to a lower level. From Ohms law, the voltage drop in volts is equal to the current in amperes. copper (noun) a reddish-brown metal used for making wires Copper is the most commonly used metal in electric engineering. brass (noun) a very hard bright yellow metal that is a mixture of copper and zinc Brass is an alloy of 50-70 per cent of copper and 30-50 per cent of zinc. lead (noun) a soft easy metal Lead is a soft-ductile metal grayish in color. tin (noun) a soft white metal is used to cover and protect iron and steel Tin is a silver-white metal, which resists the action of water and air. tungsten ( noun) a hard metal that is one of the elements used in making steel Tungsten is necessary constituent part in making steel. mercury (noun) a heavy silver white metal that is liquid at ordinary temperature Mercury is poisonous, especially its fumes.
A. Learn to recognize the following international words.
potential, difference, terminal, electric, force, free, electrons, kinetic energy, resistant, cycle, conductor, body, rheostat, resistor, ammeter, material, temperature, factor, section, meter, machine, apparatus, cable, engineering.
B. Learn the pairs of antonyms and synonyms, translate them.
below above tiny - huge useful useless liquid - solid easy difficult unexpected expected field sphere low - high full complete conductivity non-conductivity to lose to find advantage - disadvantage
C. Translate the following sentences from English into Russian, paying attention to the new lexical minimum.
D. Read the text, give it the title and explain what electromotive force, voltage, voltmeter are.
For an electric current to flow continuously around a circuit, the terminals of the energy source must be maintained at different potentials. A very close analogy is provided by two vessels filled with water to different levels and connected by a tube: water will flow from one vessel into the other as long as the difference in their levels is maintained. The factor that establishes and maintains the potential difference and causes a current to flow around a circuit against its internal and external resistance is called electromotive force (abbreviated EMF and designated by the symbol E). Electromotive force can be produced in several ways. In chemical sources of electric energy ( galvanic cells and storage battery), the EMF is set up by the action of certain chemical solutions on dissimilar metals, in electric generators it is developed by a combination of magnetic and mechanical means, in thermo cells it is set up by thermal energy. The difference of potentials at two points that causes a movement of electricity from one point to the other is called voltage. Both emf and voltage are measured in volts by means of voltmeters. The volt has several multiples and submultiples: the kilovolt, or a thousand volts, and the millivolt, or one-thousandth of a volt, being the most common ones. Voltages in the millivolt range are measured with a millivolt meter and in the kilovolt range by a kilovolt meter. In measuring the emf of a source, a voltmeter should be connected to its terminals with the external circuit open. For a measurement of the voltage of a partial circuit, a voltmeter should be connected across that portion of the circuit.
E. Choose the correct response to complete sentences.
electric current electromotive force resistivity voltage voltage drop zero
flow around a circuit against its internal and external resistance is called .. ( vemotitroelec cefor).
F. Read and translate the text, make up 7 questions to it.
Date: 2014-12-28; view: 1467
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