Interchangeability

The importance of system compatibility has long been recognized in many industries, and the automobile aftermarket industry in particular. Most replacement parts in maintenance and repair are manufactured by suppliers other than the OEM in today s automobile industry. However, in the medical device industry and aviation industry, only selected and closely controlled parts are allowed in the aftermarket to ensure good system compatibility. 

Many component parts are manufactured in accordance with the industrial standards for good system compatibility and part interchangeability. The most notable example are the standards for the bolts, nuts, and other fasteners. The diameter, type of thread, and length are all well standardized. Tables 7.2 and 7.3 summarize a few sample standards of the metric screw threads and the unified screw threads, respectively. Both systems adopt the 

Major Diameter (mm) Coarse Threads Fine Threads  

Numerous other off-the-shelf spare parts, such as tubing, bearings, and gears, are also manufactured with acceptable system compatibility in terms of fit, form, and function in the automobile and other industries. Usually they are readily available unless other regulatory requirements need to be satisfied. 

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Berlin green, FeFe(CN)mechanism postulated for the interchange of substituents in trigonal-bipyramidal 5-co-ordinate complexes, e g. PF, and its substituted derivatives. berthoUide compound Solid phases showing a range of composition. 

It reacts chemically as if it were either 1,3,5-trihydroxybenzene or the triketone of hexa-hydrobenzene. The trialkyl derivative of the hydroxy-form or the trioxime of the keto-form can be obtained from phloroglucinol by reacting in a suitable manner. In certain cases derivatives of the two forms are interchangeable. Used in printing, photography, adhesives, pharmaceuticals. 

Prepared generally by ester interchange from polyvinylacelate (ethanoate) using methanol and base also formed by hydrolysis of the acetate by NaOH and water. The properties of the poly(vinyl alcohol) depend upon the structure of the original polyvinyl acetate. Forms copolymers. Used as a size in the textile industry, in aqueous adhesives, in the production of polyvinyl acetates (e.g. butynal) for safety glasses. U.S. production 1980... 

The terms standards and specifications are constantly confused and interchanged in everyday use. The general opinion is that they are synonymous yet these two terms cover different concepts. Therefore, they — as well as the organizations that are responsible for their development — need to be defined. 

If X is put equal to a distance of, say, 100 A, then t is about 10 sec, so that, due to Brownian motion, there is a very rapid interchange of molecules between the surface and the adjacent bulk region. 

A case can be made for the usefulness of surface tension as a concept even in the case of a normal liquid-vapor interface. A discussion of this appears in papers by Brown [33] and Gurney [34]. The informal practice of using surface tension and surface free energy interchangeably will be followed in this text. 

For liquids, the last term in Eq. VIl-5 is zero, so that r = G or t = 7, since we will use G and 7 interchangeably) the same would be true of a solid if the change in area dA were to occur in such a way that an equilibrium surface configuration was always maintained. Thus the stretching of a wire under reversible... 

The wavefimction of a system must be antisynnnetric with respect to interchange of the coordinates of identical particles y and 8 if they are fermions, and symmetric with respect to interchange of y and 5 if they are bosons. 

For many-electron systems such as atoms and molecules, it is obviously important that approximate wavefiinctions obey the same boundary conditions and symmetry properties as the exact solutions. Therefore, they should be antisynnnetric with respect to interchange of each pair of electrons. Such states can always be constmcted as linear combinations of products such as... 

The tliree protons in PH are identical aud indistinguishable. Therefore the molecular Hamiltonian will conmuite with any operation that pemuites them, where such a pemiutation interchanges the space and spin coordinates of the protons. Although this is a rather obvious syimnetry, and a proof is hardly necessary, it can be proved by fomial algebra as done in chapter 6 of [1]. 

How many distinct ways of pemiuting the tliree protons are there For example, we can interchange protons 1 and 2. The corresponding syimnetry operation is denoted (12) (pronounced one-two ) and it is to be understood quite literally protons 1 and 2 mterchange their positions in space. There are obviously... 

We can apply pemiiitations successively. For example, we can first apply (12), and then (123) die net effect of doing this is to interchange protons 1 and 3. Thus we have... 

The third step follows after interchanging summation and integration and recognizing drat the N(N - l)/2 tenns in the sum are identical. The pressure follows from the relation... 

The Davies-ENDOR teclmique is based on an inversion recovery sequence (see figure B1.15.13(A ). The experiment starts by interchanging the populations of levels 1 and 3 of one of the EPR transitions of the. S-/=i... 

The identical colliding particles, each with spin s, are in a resolved state with total spinin the range (0 2s). The spatial wavefiinction with respect to particle interchange satisfies = (—1 Wavefunctions for identical particles with even or odd total spin. S are therefore symmetric (S) or antisynnnetric (A) with respect to particle... 

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