Besides the differences pointed out in the previous sections, the distributed systems also have common features, the most important deriving from the fact that the interaction between the elements occurs along a short distance. Due to this reason, the variation of the interaction intensity at the system’s borderline shall not be instantly conveyed to all the elements, but rather gradually, to one by one.
Definition 6.5.1: The transmission process of a variation of the interaction intensity from one element to another, inside a distributed system, is named propagation process (of that particular variation).
The spatial-temporal distribution of the state variation against the equilibrium level existent before the perturbation occurrence is called wave, and an isochronous surface of this wave makes-up a wave front. Taking into account these definitions, the systemic philosophy postulates the following statements:
AXIOM II (propagation axiom): A propagation process deployed outside a distributed material system (of a propagation medium) cannot exist.
Comment 6.5.1: Axiom II seems to be more like a logical conclusion after all the aspects which were depicted about the distributed material systems. However, the current science asserts that there can be propagation processes through vacuum, namely, in the absence of a support medium for this kind of process (see also section 1.5). Consequently, the above-mentioned statement has been promoted as an axiom for emphasizing once again that the assumption on the ether non-existence is a fallacy. One thing is to assign the negative result of the Michelson-Morley test to the ignorance regarding the properties of this medium, or of a model which is insufficiently elaborated for the propagation process, and other thing is the assertion that there are propagation processes of some real amounts into…nothing.
The propagation velocity of a wave depends on the parameters of that medium and it is not the topic of the present paper. It is only relevant that this velocity increases in proportion to the duration and the intensity of the interaction deployed between the system’s elements27, which is higher in case of the media having a permanent duration of this interaction. It is also worth noticing that the propagation does not involve the displacement of the medium’s elements once with the wave front, with the propagation velocity, but only low modulations of their relative positions against the equilibrium position, or of the other medium’s statistical parameters.
Comment 6.5.2: The modulation is a reversible modification (variation) process of an amount against a value which is considered (at least temporarily) as a reference value. Depending on the parameter which is modified, the amplitude, frequency, phase modulations are known facts. If the modulated parameter is the system’s position vector, a spatial modulation of the intensity of the field generated by the system might occur. It is self-understood that any modulation has also a time distribution, therefore, the modulation of a medium attribute is a process with a spatial-temporal distribution.
Another very significant feature of the propagation process is that the object28 which is conveyed (which was above-referred to as wave front) is not made-up from the same elements of the propagation medium, since its constitutive parts are always different, but the energy contained inside it (we call it the distributed attribute stockpile) is always the same - the one contained in the initial front coming from the source29.
There are different
wave types which are propagated inside a DS, depending on the local
state attribute which fluctuates or depending on the motion type
which the element might have within the distributed system. Thus, in
case of S media, for the three possible (but not free) translation
directions, the compression waves (or longitudinal) are associated,
and as for the rotation motions, the transversal (or shearing) waves
are associated. In case of L media, there could be only the
compression waves, and only in a less extent, the transversal
(viscosity) waves. As regards G media, it is obvious that there can
be only the pressure waves by means of the modulation of the free
pathway (resulting a modulation of the interactions frequency).
27 We are referring to the media composed from the same type of elements, but which are within different phases (S, L, G).
28 The wave front is a processual object, because it is a spatial distribution (at a certain moment, a temporal DP, an invariant Euler distribution) of a set of invariant properties of the propagation process (direction, velocity, contained energy etc.)
29 Not only the energy contained in the wave front is preserved; within an isotropic medium (in which the propagation velocity does not depend on the direction), the shape of the wave front (its spatial distribution) preserves the radiator shape (obviously, with its sizes in proportion to the distance towards it).
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