Approximate methods for simulation and verification of numerically controlled machining programs

Algorithms for simulation and verification of Numerically Controlled (NC) machining programs are presented. Compared to NC simulation based on conventional solid modeling systems, these models are designed to give approximate results, but with a substantial decrease in computer time. The surfaces of the part are discretized into a Surface Point Set (SPS) with a point spacing dependent on cutting tool size and shape local surface curvature and the desired accuracy of the approximate simulation. The surface-surface intersection calculations of the solid modeling approach are replaced by the intersection of the surface of the tool movement envelope with straight lines emanating from the surface points. The methods are applicable to both 3 and 5 axis machining. Samples test cases are presented, and implementation and efficiency issues are discussed.     

Variable polarisation compensator using artificial dielectrics formillimetre and submillimetre waves

A variable polarisation compensator has been designed and demonstrated experimentally at 100 GHz. The device uses two silicon plates with interlocking artificial dielectric surfaces to produce a birefringence that varies with the separation distance. The experimental results indicate a maximum differential phase-shift of 74°, and show good agreement with computer simulations     

Methods for detecting errors in numerically controlled machining ofsculptured surfaces

The numerically controlled (NC) machining of sculptured surfaces is an error-prone process often requiring several attempts before an error-free NC program is produced. A technique designed to move the NC proof process into software is described. The system outputs a color-coded graphics display of the machined surface that shows out-of-tolerance areas. To gain efficiency, surface curvature and cutting-tool size are used as inputs to a surface discretization algorithm, which guarantees that a user-defined level of simulation accuracy is achieved. The simulation time grows linearly in both desired accuracy and in the number of tool movements. In typical test cases, NC programs for complex automotive body panels were simulated and verified in CPU times that ranged between 5 and 30 minutes     

Remote fetal medicine consultation using stored ultrasound video images

Fifty-four (54) unrelated patients with Mediterranean Kaposi's sarcoma (MKS) and 8 patients members of 4 unrelated families with familial MKS were serotyped for HLA-A,B and DR antigens. The diagnosis was histologically confirmed and all patients were negative for anti-HIV antibodies. An increased frequency of HLA-B18 (44.4% vs 14.2% in the controls, p < 0.001, RR = 4.8) and HLA-DR5 (57.6% vs 37.2% in the controls, p < 0.025, RR = 2.29) was observed in the group of patients with MKS. Seven (7) of the 8 family members with FMKS possessed HLA-DR5, and the affected members in the 3 families shared a common haplotype which included HLA-DR5. These findings support the hypothesis that genetic factors linked to HLA-DR5 antigen may contribute to the pathogenesis of MKS.     

The Influence of Tunnel Geometry and Ventilation on the Heat Release Rate of a Fire

It has occasionally been observed that fires in tunnels appear to be significantly more severe than fires in the open air. A literature review has been carried out, comparing heat release data from fires in tunnels with heat release data from similar fires in the open air. A Bayesian methodology has been used to investigate the geometrical factors that have the greatest influence on heat release rate. It is shown that the heat release rate of a fire in a tunnel is influenced primarily by the width of a tunnel; a fire will tend to have a higher heat release rate in a narrow tunnel rather than in a wide tunnel. The observed relationship between heat release rate and tunnel width is presented. Results from a study investigating the variation of heat release rate with ventilation velocity for fires in tunnels are also presented. A method for making realistic estimates of the heat release rates of fires in tunnels, based on these results, is presented.     

Heat transfer analysis of the composite slab in the Cardington frame fire tests

The structural modelling of the Cardington Frame fire tests as part of the Department of Environment, Transport and Regions funded Partners in Technology project has highlighted the importance of the temperature evolution both temporally and spatially in determining the structural response. Restrained thermal expansion/contraction and thermal bowing are the main driving force behind almost all the structural phenomena witnessed in the tests.

The four British Steel fire tests carried out on the 8-storey composite steel and concrete building at Cardington have provided a wealth of information about the temperatures in the fire atmosphere and the protected and unprotected steel. Unfortunately, there is considerably less information on the temperatures attained in the concrete slab. In Tests 1–3, the temperatures through the depth of the slab have been recorded only at a few points and in terms of the structural modelling this has been just about adequate. There were no temperatures recorded in the slab in Test 4 (Office demonstration test).

The finite element, adaptive heat transfer program HADAPT has been used to model the heat transfer to the composite steel and concrete slab. HADAPT is a 2D adaptive heat transfer code capable of carrying out a nonlinear, transient, thermal analysis. The code models moisture evaporation from the pores of the concrete by assuming a phase change in the region of 100°C. The measured concrete temperatures in Tests 1–3 have been used to calibrate the model which has then been used to predict the slab temperatures in Test 4.     

Measles inclusion-body encephalitis in a child with treated acute lymphoblastic leukaemia

A child with acute lymphoblastic leukaemia, being treated in the UKALL II Trial, had while in remission an attack of measles and made a normal recovery. Four months later she developed an acute encephalopathy and died within two weeks. The brain showed mild inflammatory features and widespread inclusion bodies in neurones and glial cells. Immunofluorescence proved an infection with measles virus. Similar cases have been called SSPE; reasons are given for preferring the term "measles inclusion-body encephalitis".