Hard systems approach

How do we portray the safety assessment process in a manner that safety novices (e.g. programme managers) can understand There are various frameworks available with the Open University s (refer T840 Block 6 p. 26) hard systems approach (HSA) being particularly useful as a framework for modelling the safety assessment process. 

The HSA is a problem-solving tool that considers both quantitative and qualitative issues within the framework of the defined system. It is useful for problems which can be well defined, fairly limited in extent and with agreed objectives (defined future state, such as a system which meets its safety targets). The HSA process is iterative in nature and is summarised in Fig. 8.5 The hard systems approach can be tailored to the safety assessment process as shown in Fig. 8.6. 

Being excellent at discrete logic, PLCs are a potential candidate for implementing interlocks. Process interlocks are clearlv acceptable for implementation within a PLC. Implementation of safety interlocks in programmable electronic systems (such as a PLC) is not universally accepted. Many organizations continue to require that all safety interlocks be hard-wired, but implementing safety interlocks in a PLC that is dedicated to safety functions is accepted by some as being equivalent to the hard-wired approach. 

FIGURE 7.10 Pseudo-binary phase diagram of the water, HNO3/DMDBTDMA, dodecane system to identify the third-phase limit. Experimental points (circles) and theory (lines) obtained from Baxter sticky hard-sphere approach. The theoretical line is obtained with the experimental determination of the linear variation of the stickiness parameter tt1 versus [HN03]/[DMDBTDMA]. The different lines illustrate the impact of the error in this T-1 experimental linear law. (From C. Erlinger, L. Belloni, T. Zemb, and C. Madic, Langmuir, 15 2290-2300, 1999. With permission). 

Self-observation, observation of others, and psychoanalytic data indicate that various stimuli can produce marked reorgnaizations of ego functioning very rapdily, even though these all remain within the consensus reality definitions of "normal" consciousness. These identity states are much like d-SoCs and can be sutdied in the systems approach framework. They are hard to observe in ordinary life because of the ease and rapidity of transiton, their emotional charge, and other reasons. The isolation of knowledge and experience in various identity states is responsible for much of the psychopathology of everyday life. 

Herein, we wdl discuss several approaches that have led from molecular entities to supramolecular soft and hard systems. In particular, we will show how the molecular structure can be modified to induce the controlled self-assembly of transition metal complexes into sophisticated photoactive arrays with imusual properties derived from the structiu-e of the metal complexes and their intermolecular interactions in the ground and/or excited electronic states within the assemblies. We will start with a survey of the photophysical properties of selected transition metal complexes, followed by an overview of the aggregation mechanism they can undergo to. We will focus our attention on soft assemblies... 

In the extended system approach, additional degrees of freedom that control the quantity under consideration can be added to the system [95, 96, 103, 104], Thereby thermostats or barostats can be simulated [105-107], which provide a quality of modeling thermodynamic processes hardly reached by the stationary quantum chemical methods discussed in the previous two sections. 

Many times, the acceptance criteria also depend on the type of knowledge to be captured. Sometimes an expert-system approach is chosen as a convenience to incorporate "hard knowledge, such as inflexible rules involving regulatory requirements (Stunder and Hlinka 1989). In such cases, the expert system approach has no... 

In the systems approach, awareness is given a real and separate status. Recall the distinction between awareness and consciousness. Axoareness is that basic, obviously there but hard-to-define... 

In DPMs, each particle is tracked individually and all collisions are calculated, thus providing a more reliable and detailed representation of the fluidized bed. The model was introduced by Hogue and Newland (1994), Hoomans et al. (1996), and Tsuji et al. (1992), and it employs either a hard-sphere approach for dilute systems or a soft-sphere approach for dense fluidized beds. 

From the point of view of a high level safety analysis strategy, if the definition of a system given above is adopted, the distinction between soft/hard systems, and system failures, is neither a natural nor a useful one. Any system, regardless of its attributes and nature, must be analysed in a systematic way and the generic approach should be the same. 

This immediately establishes the requirement T = T" as a necessary condition for thermal equilibrium, which is hardly news. Also, as the system approaches its equilibrium state the entropy approaches its final maximum value—we knew that already. 

Truncation at the first-order temi is justified when the higher-order tenns can be neglected. Wlien pe higher-order tenns small. One choice exploits the fact that a, which is the mean value of the perturbation over the reference system, provides a strict upper bound for the free energy. This is the basis of a variational approach [78, 79] in which the reference system is approximated as hard spheres, whose diameters are chosen to minimize the upper bound for the free energy. The diameter depends on the temperature as well as the density. The method was applied successfiilly to Lennard-Jones fluids, and a small correction for the softness of the repulsive part of the interaction, which differs from hard spheres, was added to improve the results. 

Anotlier model system consists of polymetliylmetliacrylate (PMMA) latex, stabilized in organic solvents by a comb polymer, consisting of a PMMA backbone witli poly-12-hydroxystearic acid (PHSA) chains attached to it [10]. The PHSA chains fonn a steric stabilization layer at tire surface (see section C2.6.4). Such particles can approach tire hard-sphere model very well [111. 

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