Warm-up

Due to the absorbed photon energy in the moment of the beam admission the particles and the substrate surface warm up very fast. As a consquence of the thermal induced stresses between the relative brittle hard particles, some particles brake apart and, because of the released impulse energy, they are ejected out of the effective beam zone, transmission... 

The changes described above also allowed much easier access to the high voltage cable for routine (6-month) owner directed, service operations, and provided better upper and lower x-ray cabinet and control cabinet ventilation. With the exception of the x-ray tubes, all the individual manufactured components, on all four systems are identical. There are very subtle differences in the warm-up/start-up sequence on the x-ray controllers on the newer systems due to model/year and x-ray tube differences. The last three systems were supplied with environmental type key-boards for the image processors and base-mounted , rather than conduit-mounted exterior warning indicators. The first system was subsequently upgraded to include the better keyboard and the external warning appliances/features. 

These systems have been operated in extremely low quality (and radioactivity contaminated) industrial environments for the past several years without any major equipment or component failures. Utilizing specialized operating/warm-up procedures, they have operated in low grade, out-of-doors, dust ridden, rain-soaked, industrial environments at temperature ranges which greatly exceed the original equipment manufacturers (OEM) specified limits. The systems have been successfully operated at ambient temperatures of minus 10 to plus 103 degrees Fahrenheit without any pre-mature or un-anticipated equipment failures. 

Chlorobenzene. Prepare a solution of phenyldiazonium chloride from 31 g. (30 -5 ml.) of aniUne, 85 ml. of concentrated hydrochloric acid, 85 ml, of water, and a solution of 24 g. of sodium nitrite in 50 ml. of water (for experimental details, see Section IV,60). Prepare cuprous chloride from 105 g. of crystallised copper sulphate (Section 11,50,1), and dissolve it in 170 ml. of concentrated hydrochloric acid. Add the cold phenyl diazonium chloride solution with shaking or stirring to the cold cuprous chloride solution allow the mixture to warm up to room temperature. Follow the experimental details given above for p-chlorotoluene. Wash the chlorobenzene separated from the steam distillate with 40 ml. of 10 per cent, sodium hydroxide solution (to remove phenol), then with water, dry with anhydrous calcium chloride or magnesium sulphate, and distil. Collect the chlorobenzene (a colourless liquid) at 131-133° (mainly 133°), The yield is 29 g. 

I) Hydroquinone dIacetate may be prepared as follows. Add I drop of concentrated sulphuric acid to a mixture of 55 g. of hydroquinone and 103 g. (05-5 ml.) of A.R. acetic anhydride in a 500 ml. conical flask. Stir the mixture gently by hand it warms up rapidly and the hydroquinone dissolves. After 5 minutes, pour the clear solution on to 400 ml. of crushed ice. Alter with suction and wash with 500 ml. of water. Recrystallise the solid from 50 cent, ethanol by weight (ca. 400 ml. are required). The yield of pure hydroquinone diacetate, m.p. 122°, is 89 g. 

Dimethylaminomethylindole (gramine). Cool 42 5 ml. of aqueous methylamine solution (5 2N ca. 25 per cent, w/v) contained in an 100 ml. flask in an ice bath, add 30 g. of cold acetic acid, followed by 17 -2 g. of cold, 37 per cent, aqueous formaldehyde solution. Pour the solution on to 23 -4 g. of indole use 10 ml. of water to rinse out the flask. Allow the mixture to warm up to room temperature, with occasional shaking as the indole dissolves. Keep the solution at 30-40° overnight and then pour it, with vigorous stirring, into a solution of 40 g. of potassium hydroxide in 300 ml. of water crystals separate. Cool in an ice bath for 2 hours, collect the crystalline solid by suction flltration, wash with three 50 ml. portions of cold water, and dry to constant weight at 50°. The yield of gramine is 34 g. this is quite suitable for conversion into 3-indoleacetic acid. The pure compound may be obtained by recrystaUisation from acetone-hexane m.p. 133-134°. 

When power is appHed to an electronic scale, it warms up and is somewhat unstable until thermal equiHbrium is reestabHshed. The manufacturer s recommendations with regard to warm-up period should be followed. 

Use Equipment Only When deeded. Start morning warm-up no earHer than necessary and do not use outside air for ventilation until the building is occupied. Use minimum amounts of outdoor air according to reference 8. Supply heat at night only to maintain a temperature above 13°C. Supply Heating and Cooling from the Most Efficient Source. 

Consequendy, convective heat transfer determines the intensity of warming up and ignition. In addition, convective heat transfer also plays an important part in the overall dame-to-surface transmission. The reaction of gases is greatiy accelerated by contact with hot surfaces and, whereas the reaction away from the walls may proceed slowly, reaction at the surface proceeds much more rapidly. 

It is generally felt that fuels which have values of DI below 570 when Tis in °C (1200 when Tis in °F) provide good warm-up driveabiUty performance. 

DP systems can be shut down when not in use to conserve energy. If a Hquid-nitrogen trap is incorporated, the manner in which this trap is warmed up and the DP is cooled down should be deterniined by the presence or absence of a valve between the chamber and the Hquid-nitrogen trap. In critical systems, this head valve can be included in order to permit rapid shutdown and rapid return to operation. The assertion that dry nitrogen gas can be used to sweep contamination from traps and pumps in such manner that oil contamination is prevented from mnning counter to the nitrogen-sweeping flow direction is questionable. Proper placement of valves can eliminate the need of a sweep gas. 

H. Yamamoto and co-workers, Warm-Up Characteristics of Thin Wall Honeycomb Catalysts, SAE 910611, Society of Automotive Engineers,... 

Well, that is the case at the low temperature, when the rubber has a proper modulus of a few GPa. As the rubber warms up to room temperature, the Van der Waals bonds melt. (In fact, the stiffness of the bond is proportional to its melting point that is why diamond, which has the highest melting point of any material, also has the highest modulus.) The rubber remains solid because of the cross-links which form a sort of skeleton but when you load it, the chains now slide over each other in places where there are no cross-linking bonds. This, of course, gives extra strain, and the modulus goes down (remember, E = [Pg.61]

When crystais grow they give out iatent heat. If this is not removed from the interface then the interface wiii warm up to T, and soiidification wiii stop. In practice, latent heat will be removed from the interface by conduction through the solid and convection in the liquid and the extent to which the interface warms up will depend on how fast heat is generated there, and how fast that heat is removed. 

In metals the situation is quite the opposite. The spherical atoms move easily from liquid to solid and the interface moves quickly in response to very small undercoolings. Latent heat is generated rapidly and the interface is warmed up almost to T, . The solidification of metals therefore tends to be heat-flow controlled rather than interface controlled. 

An idea of the possibilities is given by the old high-school chemistry experiment with sulphur crystals ("flowers of sulphur"). A 10 ml beaker is warmed up on a hot plate and some sulphur is added to it. As soon as the sulphur has melted the beaker is removed from the heater and allowed to cool slowly on the bench. The sulphur will... 

Please notice that in a well-ventilated laboratory and a pressure cell, these experiments can be executed safely. In seven years of graduate research activity at the Chemical Engineering Department of the University of Akron, only one catalyst ignition and one real CO alarm occurred. Several false CO alarms were sounded until someone noticed that they always happened about 2 30 PM. As it turned out, one maintenance employee parked his old car right in front of the air intake to the lab ventilation. He warmed up his car for a while before he started to go home after his shift, and the motor exhaust gas set off the false alarms. 

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