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D(3He,p)4He and D(d,p)3H fusion in a small plasma focus operated in a deuterium helium-3 gas mixture

Springham S., Sim T., Rawat T., Lee P., Patran A., Shutler P., Tan T., Lee S.

Nukleonika

2006

Vol. 51, nr 1

47-53

Abstract A 3 kJ plasma focus was operated with a 3He-D2 gas mixture, with partial pressures in the ratio of 2:1, corresponding to an atomic number ratio of 1:1 for 3He and D atoms. The fusion reactions D(3He,p)4He and D(d,p)3H were measured simultaneously using CR-39 polymer nuclear track detectors placed inside a pinhole camera positioned on the forward plasma focus axis. A sandwich arrangement of two 1000 mi m thick CR-39 detectors enabled the simultaneous registration of two groups of protons with approximate energies of 16 MeV and 3 MeV arising from the D(3He,p)4He and D(d,p)3H reactions, respectively. Radial track density distributions were obtained from each CR-39 detector and per-shot average distributions were calculated for the two groups of protons. It is found that the D(3He,p)4He and D(d,p)3H proton yields are of similar magnitude. Comparing the experimental distributions with results from a Monte Carlo simulation, it was deduced that the D(3He,p)4He fusion is concentrated close to the plasma focus pinch column, while the D(d,p)3H fusion occurs relatively far from the pinch. The relative absence of D(d,p)3H fusion in the pinch is one significant reason for concluding that the D(3He,p)4He fusion occurring in the plasma focus pinch is not thermonuclear in origin. It is argued that the bulk of the D(3He,p)4He fusion is due to energetic 3He2+ ions incident on a deuterium target. Possible explanations for differing spatial distributions of D(3He,p)4He and D(d,p)3H fusion in the plasma focus are discussed.

Generating personalized anatomy-based 3D facial models from scanned data

Zhang Y., Sim T., Tan C. L.

Machine Graphics and Vision

2005

Vol. 14, No. 1

3-28

This paper presents a new method for reconstructing animatable, anatomy-based human facial models from scanned range data. Our method adapts a prototype model that is suitable for physically-based animation to the geometry of a specific person's face with minimal user intervention. The prototype model has a known topology and incorporates a multi-layer structure of the skin, muscles, and skull. Based on the series of measurements between a subset of anthropometric landmarks specified on the prototype model and the scanned surface, an automated global alignment adapts the size, position, and orientation of the prototype model to align it with the scanned surface. In the skin layer adaptation, The generic skin mesh is represented as a dynamic deformable model which is subjected to internal force stemming from the elastic properties of the surface and external forces generated by the scanned data points and features. We automatically deform the underlying muscle layer consisting of three types of muscle models. A set of automatically generated skull feature points is then transformed based on the deformed external skin and muscle layers. The new positions of these feature points are used to drive volume morphing applied to the skull template for skull fitting. With the adapted multi-layer anatomical structure, the reconstructed model not only resembles the shape of the individual's face but can also be animated instantly using the muscle and jaw parameters.