Weak link concept

The factors controlling the mechanical behavior of polymer-coupling agent-metal oxide systems have been discussed in terms of the weakest link in a chain concept. Determination of the locus of failure and thus the weak link is not usually reliable by visual inspection, and surface roughness can cause misleading spectroscopic results if failure is near an interface. 

Based on the operating experience of nuclear power plants in the Russian Federation one can draw a conclusion that in the course of decision-making by the operator the weak link is the stage of analyzing and understanding the situation on the basis of the received information. To help operation personnel in the main control room the concept of critical functions and safety parameters has been developed and implemented abroad at a series of Western nuclear power plants. 

It must be noted here that other explanations have been proposed for the reinforcing effect of CB. Blanchard considered that CB strongly modifies fhe nature of the elastomer network with, amongst other features, strong and weak links between rubber segments and appropriate sites at the surface of particles. Recent considerations are close to this concept, as we shall see later. 

For systems that are nearly linear or time-variant, the concept of the impulse (complex frequency) response is still applicable. For weakly non-linear systems the characterization can be extended by including measurements of the non-linearity (noise, distortion, clipping point). For time-variant systems the characterization can be extended by including measurements of the time dependency of the impulse response. Some of the additional measurements incorporate knowledge of the human auditory system which lead to system characterizations that have a direct link to the perceived audio quality (e.g. the perceptually weighted signal to noise ratio). 

An electrochemical method projected for the determination of the effective volume of a colloidally dispersed polyelec-trolyte phase in aqueous media was evaluated. Experiments with the highly flexible Sephadex (carboxymethyldextran) gel and the more rigidly cross-linked polymethacrylic acid resin were performed for this purpose. With the well-defined resin (gel) phase it was possible to measure the polymer volume as a function of every experimental condition used to test fully the fundamental concepts on which the method is based. The results substantiate the validity of concepts developed. Application of this method for estimating the effective volume of weakly acidic (basic) polymers in solution seems worthy of further consideration. However, some modification of the treatment of the electrochemical data is necessary for polymeric sols, and this aspect is discussed briefly. 

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