Hierarchical system

The concentration of all automation functions within a single computer (Section 7.19.1) may be possible for a very simple plant, but this type of configuration is inefficient for more complex processes for which there could be many thousands of connections between plant and computer. Currently, small industrial processes are controlled by a hierarchical architecture consisting of a central computer (usually a minicomputer), which is used to solve central automation problems, together with a series of peripheral computers (generally microprocessors which are called front-end computers) which control different sections of the plant (Fig. 7.104a). This type of architecture is termed a decentralised computer system. 

A two-level structure is inadequate, however, for large-scale plants due to overloading of the central computer. In this case, a three-stage hierarchy is employed with intermediate (or group) computers running some of the duties which are common to all the local microprocessors (Fig. 7.1046). 

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A hierarchical system is the simplest type ofdatabase system. In this form, the var-iou.s data typc.s also called entities (sec figure 5-,3) arc as.signcd. systematically to various levels (Figure 5-5). The hierarchical system is represented as an upside-down tree with one root segment and ordered nodes. Each parent object can have one or more children (objects) but each child has only one parent. If an object should have more than one parent, this entity has to be placed a second time at another place in the database system. 

Relational databases can store unlimited numbers of results for every sample and unlimited samples for every request. The advantage of a relational DBMS over a more traditional hierarchical system, in which data sets may contain other data sets, is that the design of the database only has to consider relationships between data elements, not the number of instances for any given variable. 

Figure 2.2 Classification of different types of porous materials, (a) A purely microporous zeolite is considered as a non-hierarchical system according to the single level of porosity, (b) Fragmentation of the zeolite into nanocrystals engenders a network of mesopores constituting the intercrystalline space, leading to an interconnected hierarchical system. Intraconnected...

As zeohtes are known for their weU-defined micropore size and the associated ability to host shape-selective transformations, it is of distinct importance that the micropores in the hierarchical systems have the same size as those in the... 

As shown in Table 2.1, the improved catalytic performance of alkaline-treated zeolites compared to the parent purely microporous counterparts has been demonstrated decidedly by different groups active in academia and in industry. The positive effect is reflected in the enhanced activity, selectivity, and/or lifetime (coking resistance) of the hierarchical systems. The examples listed embrace not only a variety of zeohte topologies (MFl, MOR, MTW, BEA, and AST) but also reactions involving hghter hydrocarbons as well as bulky molecules. This illustrates the potential of the desihcation treatment, although more work is to be done in optimizing the catalytic system for the wide variety of applications. 

Findeisen, W., et al., Control and Coordination in Hierarchical Systems. Wiley, New York, 1980. 

G.N. Lance and W.T. Williams, A general theory of classificatory sorting strategies. 1. Hierarchical systems, Comput. J., 9 (1967) 373-380. 

The nanometer- to micrometer-scale dimensions of supramolecular assemblies present many challenges to rigorous compositional and structural characterization. Development of adequate structure-property relationships for these complex hierarchical systems will require improved measurement methods and techniques. The following areas constitute critical thrusts in instrument development. 

The corresponding hierarchical system of models may have the following sequence [3,61] ... 

The approaches considered allow modeling of the primary texture of PS and the processes, limited by individual PBUs that mainly correspond to level III and partially to level IV in the hierarchical system of models (see Section 9.6.3). PBUs are identical in regular PSs, and simulation of numerous processes may be reduced to analysis of a process in a single PBU/C or PBU/P. An accurate modeling of the processes in irregular PSs requires the studies of the properties of structure and properties of the ensembles (clusters) of particles and pores (level IV of the system of models) and the lattices of such clusters (levels V to VII of the system of models). Let us consider the composition of clusters on the basis of fractal [127], and the lattices on the basis of percolation [8] theories. 

IPEC or hydrogen-bonded complexes may form not only between mutually interacting polymer blocks but also between a polymer block and low-MW molecules. Complexes between surfactants and block copolymers have been investigated for the formation of micelles. As illustrated by the work of Ikkala and coworkers [313], one of the major interests of these systems is that they combine two different-length scales of supramolecular organizations, i.e., the nanometer-scale organization of the (liquid) crystalline surfactant molecules and the ten-nanometer scale relative to block copolymers. This gives rise to the so-called hierarchical systems. The field of (block)... 

The relationship between central and peripheral oscillators is different in flies and mammals. In mammals, these oscillators form a hierarchy in which the central oscillator, which resides in the suprachiasmatic nucleus (SCN), functions as a master clock that is entrained by photic signals from the eye, and in turn drives subservient peripheral oscillators via humoral signals (Moore et al 1995, Yamazaki et al 2000, Kramer et al 2001, Cheng et al 2002). In contrast, both central and peripheral oscillators operate autonomously and are directly entrainable by light in Drosophila (Plautz et al 1997), thus obviating the need for a hierarchical system. Our results support the concept of independent oscillators in flies since central (sUN ) oscillators are not necessary for olfaction rhythms and local oscillators in antennae appear to be sufficient. 

The therapy model uses elements of both structural and strategic family therapy. Structural family therapy derives its name from the perceived importance of family composition, particularly as a hierarchy, and how this hierarchical system is organised. For example, a family with a weak and ineffectual father would be subject to an imbalance in family structure. The therapist s main objective is to identify the imbalance and to intervene by emphasising the importance of the father and his role in the family, that is, elevating his importance. Structural family therapy is widely associated with Salvador Minuchin, who used it extensively in the treatment of anorectic families . Only a cursory summary is presented here. Interested readers will find these techniques covered more fully in Minuchin and Fishman (1981). 

Most of the neuronal systems in the CNS can be divided into two broad categories hierarchical systems and nonspecific or diffuse neuronal systems. 

Although there is a great variety of synaptic connections in these hierarchical systems, the fact that a limited number of transmitters are used by these neurons indicates that any major pharmacologic manipulation of this system will have a profound effect on the overall excitability of the CNS. For instance, selectively blocking GABAa receptors with a drug such as... 

Neuronal systems that contain one of the monoamines—norepinephrine, dopamine, or 5-hydroxytryptamine (serotonin)— provide examples in this category. Certain other pathways emanating from the reticular formation and possibly some peptide-containing pathways also fall into this category. These systems differ in fundamental ways from the hierarchical systems, and the noradrenergic systems serve to illustrate the differences. 

Whatever the answer to this question, it seems to me reckless to propose that any part of the brain operates independently of any other. This is especially true of a hierarchical system like the reticular thalamic one that controls forebrain activation so prominently. Of course, the several neuronal participants in this hierarchical system will occasionally become dissociated so that now the cortex, now the thalamus, now the brain stem takes the lead in state component generation, but in order for state control to have any reliability, the flow of control has to be from the bottom up. 

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