Browsing by Subject "decomposition"

Design embraces several disciplines dedicated to the production of artifacts and services. These disciplines are quite independent and only recently has psychological interest focused on them. Nowadays, the psychological theories of design, also called design cognition literature, describe the design process from the information processing viewpoint. These models co-exist with the normative standards of how designs should be crafted. In many places there are concrete discrepancies between these two in a way that resembles the differences between the actual and ideal decision-making. This study aimed to explore the possible difference related to problem decomposition. Decomposition is a standard component of human problem-solving models and is also included in the normative models of design. The idea of decomposition is to focus on a single aspect of the problem at a time. Despite its significance, the nature of decomposition in conceptual design is poorly understood and has only been preliminary investigated. This study addressed the status of decomposition in conceptual design of products using protocol analysis. Previous empirical investigations have argued that there are implicit and explicit decomposition, but have not provided a theoretical basis for these two. Therefore, the current research began by reviewing the problem solving and design literature and then composing a cognitive model of the solution search of conceptual design. The result is a synthetic view which describes recognition and decomposition as the basic schemata for conceptual design. A psychological experiment was conducted to explore decomposition. In the test, sixteen (N=16) senior students of mechanical engineering created concepts for two alternative tasks. The concurrent think-aloud method and protocol analysis were used to study decomposition. The results showed that despite the emphasis on decomposition in the formal education, only few designers (N=3) used decomposition explicitly and spontaneously in the presented tasks, although the designers in general applied a top-down control strategy. Instead, inferring from the use of structured strategies, the designers always relied on implicit decomposition. These results confirm the initial observations found in the literature, but they also suggest that decomposition should be investigated further. In the future, the benefits and possibilities of explicit decomposition should be considered along with the cognitive mechanisms behind decomposition. After that, the current results could be reinterpreted.

In Norway spruce (Picea abies) dominated mineral soil sites, the polypore Heterobasidion parviporum often causes severe decay problems (butt rot, root rot). Not much is however known on the ability of H. parviporum to cause decay losses in peatland. The purpose of this study was to answer some fundamental question: 1) Is H. parviporum able to cause decay losses in drained mires? 2) Is there an effect of other soil microbes during saprotrophic growth of Heterobasidion on peat soil? 3) What are the potential inhibitory effects of microbes inhabiting peat soil on growth of Heterobasidion? For the decay study, wood discs (P. abies) in mesh bags were buried at the different forest sites; mineral soil and peatlands (including drained mire and undrained mire). The amount of weight loss was documented after four months. The study was repeated in vitro by autoclaving soil samples from these sites together with wood discs followed by inoculation with H. parviporum. On mineral soil, H. parviporum decayed spruce (P. abies) wood disc much more than on non-drained pristine mire. On drained (ditched) mire, no significant difference in the weight loss was observed. H. parviporum grew significantly more on the sterilized soil and decayed more wood, compared to non-sterilized soil. The results suggested that secreted metabolites in the unsterilized soil may be able to significantly suppress saprotrophic growth of H. parviporum. In the fungal growth inhibition experiment, water- and acetone-soluble substances were extracted from the soil with acetone and water. No fungal growth inhibiting substances were detected from the various peat soils or mineral soils.