Top-down decomposition

The overall PPM is organized along the classification dimension of four layers application model layer, external model layer, internal model layer and basic model layer. In a hierarchical top-down decomposition, each layer uses concepts from its direct upper layer and enriches them with additional aspects. 

In order to keep the whole CIM system integrated, in the functional and logical model design, the overall system design follows the top-down decomposition principle. The top level and general functions should be first considered, then decomposed to low-level and detailed operations. 

For computer based system applications, top-down decomposition, levels of abstraction and modular stracture are important concepts for coping with the problems of nnavoidable complexity. They not only allow the system developer to tackle several smaller, more manageable problems, but also allow a mote effective review by the verifier. The logic behind the system modularization and the definition of interfaces shonld be made as simple as possible (for example by applying information hiding (see Section 3.3.4 of Ref. [4])). 

If these systems are themselves too complex most often one again thinks in terms of their subsystems. This process of looking for simpler subsystems within subsystems is repeated as many times as necessary. The process is called top down decomposition, and it gives rise to notion of levels of abstraction. It is the only known means of analysing complex systems. 

Figure 14.10. Principal component analysis of Py-FI mass spectra of (a) cold and (b) hot water extracts from the sequence of organic litter layers Oi-Oe-Oa in a beech stand (Fagus sylvat-ica) obtained before (-pre) and after (-post) aerobic incubation. The arrows indicate changes due to progressive decomposition top-down in the litter profile. Reprinted from Landgraf, D., Leinweber, P, and Makeschin, F. (2006). Cold and hot water extractable organic matter as indicators of litter decomposition in forest soils. Journal of Plant Nutrition and Soil Science 169,76-82, with permission of Wiley-VCH.

The software design concepts such as modular, top-down, and decomposition of the design requirements have been used in the computer science fields for over 20 years. However, the application of these concepts can vary. 

Hydrogen decomposition desorption recombination (HDDR) process is the only top-down industrial process used for the preparation of coercive nanoparticles. This process applied to rare-earth transition-metal (RE-TM) alloys consists in heating the concerned alloy under hydrogen until it decomposes into a fine mixture of RE-hydride and TM. The hard magnetic phase is recombined with a much finer microstructure. This process was first developed to convert 100 microns sized cast Nd2Fei4B grains into 200-300 nm crystallites [18, 19]. Later, it has been applied to other RE-TM alloys [20, 21]. Recently, a new variation of this process has been developed towards developing texture in the final materials [22], It is briefly described below. 

Modeling Method for Function View Function view modeling normally uses the top-down structural decomposition method. The function tree is the simplest modeling method, but it lacks the links between different functions, especially the data flow and control flow between different functions, so it is generally used to depict simple function relationships. In order to reflect data and control flow relationships between different functions, SADT and IDEFO (Colquhoun and Baines 1991) methods are used to model function view. The IDEFO formalism is based on SADT, developed by Ross (Ross 1985). 

The PSSA is the top-down part of the safety process - this is where architecture is established based on the FHA knowledge FDALs are decomposed to the point they allocated to items, at which point they become IDAL targets. There may be several layers of architectural decomposition here. In simple terms the PSSA proposes what we are going to do about the things that can go wrong. 

Such decomposition and the consolidation in the system integration (allocation of multiple functions to one element and the development of new common functions) will have to be necessary in all system levels since only limited resources can be provided in the systems. Here we speak of a top down analysis, which later... 

Numerous methods exist for the preparation of transition metal(O) nanoparticles as recently reviewed [19,41-43]. Briefly, there are two general approaches for the preparation of metal nanoparticles "top-down" and "bottom-up" approaches. The "top-down" approach involves the thermal, chemical, or mechanical disintegration of large particles of bulk metal into nanoparticles [44-46], while the more common and practical "bottom-up" approach involves first the generation of metal atoms from the reduction or decomposition of a precursor followed by... 

The first step towards the development of chitosan-coated lONP nanoparticles is the synthesis of uniformly shaped and sized lONP nanoparticle cores. Over the years, many approaches have been evaluated for the synthesis of lONP cores [21], These approaches can be generally divided into two groups top-down (mechanical attrition) and bottom-up (chemical synthesis) approaches [22], Of the two routes, the chemical synthesis approach is generally favored as it is better suited to production of nanoparticles with uniform size and shape (typical deviadOTi is less than 10% of the nanoparticle batch) [23]. The chemical synthesis approach can be further subcategorized into two major chemical processes coprecipitation and thermal decomposition. Both chemical processes have been exploited for the development of chitosan-coated lONPs however, each process has its own advantages and limitations, as discussed below. 

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