993 resultados para Nc


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Three sequential hurricanes, Dennis, Floyd, and Irene, affected coastal North Carolina in September and October 1999. These hurricanes inundated the region with up to 1 m of rainfall, causing 50- to 500-year flooding in the watershed of the Pamlico Sound, the largest lagoonal estuary in the United States and a key West Atlantic fisheries nursery. We investigated the ecosystem-level impacts on and responses of the Sound to the floodwater discharge. Floodwaters displaced three-fourths of the volume of the Sound, depressed salinity by a similar amount, and delivered at least half of the typical annual nitrogen load to this nitrogen-sensitive ecosystem. Organic carbon concentrations in floodwaters entering Pamlico Sound via a major tributary (the Neuse River Estuary) were at least 2-fold higher than concentrations under prefloodwater conditions. A cascading set of physical, chemical, and ecological impacts followed, including strong vertical stratification, bottom water hypoxia, a sustained increase in algal biomass, displacement of many marine organisms, and a rise in fish disease. Because of the Sound's long residence time (≈1 year), we hypothesize that the effects of the short-term nutrient enrichment could prove to be multiannual. A predicted increase in the frequency of hurricane activity over the next few decades may cause longer-term biogeochemical and trophic changes in this and other estuarine and coastal habitats.

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[Brown shooting over North Carolina State's Daria Parker, 2nd round of NVAA Tournament at Raleigh, NC]

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The changing face of industry due to the adoption of `New Technology' is briefly discussed, as are the corresponding structural changes in the workforce. The adoption of NC machinery is identified as one of the major innovations affecting the structure of industry. The development of NC machinery, and of relevant programming techniques are reviewed, and the problems arising from its initial sponsorship by the aerospace industry are highlighted. The process of its subsequent diffusion into industry is reviewed. Skill levels adopted for NC use in Britain and Germany are discussed, and analysed to create a structural pattern. These classifications of skill levels are then used to examine the organisational structures adopted by companies utilising NC machines. The greater use made of higher level shop floor skills by German companies is discussed. The results of two surveys of the use made of NC by companies in the North East of England are presented. Effective company organisation for NC use is described, and lack of foresight is shown to lead to vulnerability problems where skills can become concentrated in a few key people. This led to closure of a company in one instance. It is shown that small sub-contract companies have adopted a highly skilled shop floor workforce, and that they have survived in the present hostile economic environment, whilst companies who have used NC to de-skill the shop floor contracted dramatically in the same period. The lack of awareness of the potential for reviewing the product design in relation to the flexibility of NC, so leading to reductions in work in progress levels, is highlighted. Recommendations for skill structures appropriate to various sized companies and suitable training programs are presented to ensure that the full potential of NC machinery is achieved.

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Conventional methods of form-roll design and manufacture for Cold Roll-Forming of thin-walled metal sections have been entirely manual, time consuming and prone to errors, resulting in inefficiency and high production costs. With the use of computers, lead time can be significantly improved, particularly for those aspects involving routine but tedious human decisions and actions. This thesis describes the development of computer aided tools for producing form-roll designs for NC manufacture in the CAD/CAM environment. The work was undertaken to modernise the existing activity of a company manufacturing thin-walled sections. The investigated areas of the activity, including the design and drafting of the finished section, the flower patterns, the 10 to 1 templates, and the rolls complete with pinch-difference surfaces, side-rolls and extension-contours, have been successfully computerised by software development . Data generated by the developed software can be further processed for roll manufacturing using NC lathes. The software has been specially designed for portability to facilitate its implementation on different computers. The Opening-Radii method of forming was introduced as a subsitute to the conventional method for better forming. Most of the essential aspects in roll design have been successfully incorporated in the software. With computerisation, extensive standardisation in existing roll design practices and the use of more reliable and scientifically-based methods have been achieved. Satisfactory and beneficial results have also been obtained by the company in using the software through a terminal linked to the University by a GPO line. Both lead time and productivity in roll design and manufacture have been significantly improved. It is therefore concluded that computerisation in the design of form-rolls for automation by software development is viable. The work also demonstrated the promising nature of the CAD/CAM approach.