Integration of CAD/CAm as seen from the production planners point of view

CAD/CAm is supposed to be one of the new tools to obtain increased productivity and flexibility in mechanical engineering. However, most of the existing systems are still far from satisfying the users with respect to “human-like” communication. Most of the systems are either CAD or CAM oriented. To reach a real step forward, integration and better user-communication is needed. One of the first tasks to be performed after the design phase is process planning. The purpose of this planning is to select processes and operations for an optimal production. This is a creative task and is therefore dependent on long experience and very skilled planners. The article describes process planning in general and communication with CAD in particular. Some new developments using an integrated product model are described.     

The HIV-epidemic in Norway 1996--mainly heterosexual transmission

Up to 1996, a total of 1,537 individuals had been reported as having HIV infection in Norway (population 4.3 million). 511 of these had developed AIDS and 410 had died from AIDS. 223 persons had acquired HIV heterosexually. Less than a fifth of these had acquired the infection from persons who themselves had been infected with HIV heterosexually in Norway. Named testing of pregnant women, recruits and blood donors confirms the limited spread of HIV. We estimate that the annual incidence of heterosexually acquired HIV infection has remained at 20-30 for the last ten years. Earlier prognoses for the epidemic in Norway were grossly erroneous, mainly owing to lack of knowledge about the factors determining the spread of HIV. Given the low rate of transmission of the virus and the sexual behaviour of Norwegians, there was never any real danger of a large heterosexual HIV epidemic in this country. The future efforts to combat the epidemic should focus on maintaining features that make Norwegian society less vulnerable to HIV.     

Amorphous-crystalline silicon junctions

High barriers are observed in amorphous-p-type-silicon junctions, resulting in good rectification. No significant barriers are detected in amorphous-n-type-Si junctions. A simple model is also presented to describe the junction.     

Results from three models compared to full-scale tunnel fires tests

Information from full-scale fire tests are gathered and systemised. The knowledge from these tests is used as input to three different models, ranging from a simple spreadsheet model to advanced computational fluid dynamics (CFD) modelling, for calculating the temperature in the smoke layer. The deviation between the fire tests and the computed results is described and an evaluation of how this may influence the use of the models is discussed from the point of view of risk analysis.     

Dynamic distinct-element analysis of the 800 m high Åknes rock slope

The seismic stability of the Åknes rock slope, western Norway, was analysed by using the distinct element code UDEC (Universal Distinct Element Code). The slope poses a threat to the region as a sudden failure may cause a destructive tsunami in the fjord. The dynamic input was based on earthquakes with return periods of 100 and 1000 years, and in most models the input shear wave was a harmonic function (sine wave). Models with depths of the sliding surface up to 200 m and with ground water conditions derived from site investigations were analysed, as well as models with ground water conditions assumed from possible future draining of the slope. The analyses indicate that an earthquake with a return period of 1000 years is likely to trigger sliding to great depth in the slope at the present ground water conditions and that the slope will be stable if it is drained. The analyses also indicate that sliding is not likely to be triggered by an earthquake with a return period of 100 years at the present ground water conditions.     

Micro-fibre and ultra-micro-fibre cloths, their physical characteristics, cleaning effect, abrasion on surfaces, friction, and wear resistance

The properties of 12 micro-fibre cloths and two ultra-micro-fibre cloths were studied and compared with conventional cleaning methods. The cloths made from micro-fibre and ultra-micro-fibre had very good cleaning effect. Scrubbing Plexiglas caused pitting and scratch marks on the Plexiglas surface with the largest damage being caused in dry condition. All the cloths tested were wear resistant. Most of the cloths showed high friction against the surfaces in damp condition. Micro- and ultra-micro-fibre cloths are good alternatives to conventional methods for cleaning interior surfaces. Furthermore, good cleaning results can be achieved without any use of polluting cleaning chemicals.     

Uncertainty analysis of tunnel squeezing for two tunnel cases from Nepal Himalaya

Weak rocks such as shale, slate, phyllite and schist, and the rock mass of weakness/fault zones are incapable of sustaining high tangential stress. Severe tunnel squeezing is therefore common in the tectonically active Himalayan rock mass and is one of the major areas of concern regarding stability. A reliable prediction of the extent of squeezing is essential so that a strategy can be established regarding stabilizing measures and for optimizing the support well in advance (during planning and design). In this paper, a probabilistic approach to uncertainty analysis that focuses on the effect of the variations in each input parameter of squeezing is used for analyzing and predicting the extent of tunnel squeezing for two tunnel cases in Nepal; Kaligandaki “A” (completed) and Middle Marsyangdi (under construction). A semi-analytical method suggested by Hoek and Marinos [Predicting tunnel squeezing problems in weak heterogeneous rock masses. Tunnels Tunnell Int, 2000; 32(11 and 12): 45–51 and 34–36] for predicting squeezing, an empirical formula proposed by Panthi [Analysis of engineering geological uncertainties related to tunnelling in Himalayan rock mass conditions. PhD thesis, Department of Geology and Mineral Resources Engineering. Norwegian University of Science and Technology (NTNU), Norway, 2006] and the Palisade's 2002 version of @Risk statistical software program have been used for the uncertainty analysis. The analysis results for Kaligandaki indicate fairly good correlation between predicted and actually measured squeezing. The same approach has been used for predicting the degree of tunnel squeezing at Middle Marsyangdi tunnel. It is concluded that the methodology proposed in this paper has potential for predicting the squeezing of future tunnel projects in weak rock mass conditions.     

Numerical analysis of stresses and displacements for the Tafjord slide, Norway

Numerical modelling has been used for analyzing stresses and displacements for the very steep and more than 1,000 m high Heggura rock slope near Tafjord, Norway where a disastrous 3 million m³ rock slide occurred in 1934. It is shown that very anisotropic stresses exist near the slope surface and displacements of the remaining slope as result of the 1934 slide have been calculated to up to 210 mm. Such considerable displacements are believed to have a significant impact on the present and future stability of the Heggura slope.