Relativistic free-particle quantization on the light-front: New aspects

We use the light-front machinery to study the behavior of a relativistic free particle and obtain the quantum commutation relations from the classical Poisson brackets. We argue that the usual projection onto the light-front coordinates for these from the covariant commutation ralations does not reproduce the expected results.Comment: To appear in the proceedings "IX Hadron Physics and VII Relativistic Aspects of Nuclear Physics: A Joint Meeting on QCD and QGP, Hadron Physics-RANP,2004,Angra dos Reis, Rio de Janeiro,Brazi

Surprises in the relativistic free-particle quantization on the light-front

We use the light front ``machinery'' to study the behavior of a relativistic free particle and obtain the quantum commutation relations from the classical Poisson brackets. We argue that their usual projection onto the light-front coordinates from the covariant commutation relations show that there is an inconsistency in the expected correlation between canonically conjugate variables ``time'' and ``energy''. Moreover we show that this incompatibility originates from the very definition of the Poisson brackets that is employed and present a simple remedy to this problem and envisages a profound physical implication on the whole process of quantization.Comment: 13 page

Surveillance on the light-front gauge fixing Lagrangians

In this work we propose two Lagrange multipliers with distinct coefficients for the light-front gauge that leads to the complete (non-reduced) propagator. This is accomplished via $(n\cdot A)^{2}+(\partial \cdot A)^{2}$ terms in the Lagrangian density. These lead to a well-defined and exact though Lorentz non invariant light front propagator.Comment: 7 pages. This is an improved version of hep-th/030406

Effect of nitrogen in backing gas on duplex root weld properties of heavy-walled pipe

Duplex stainless steels are increasingly used for offshore subsea components as the technology allows for deeper recovery of oil and gas reserves. Alloy UNS S31803 (EN 1.4462/UNS S32205) combines high strength with good resistance to pitting and crevice corrosion. This grade is alloyed with nitrogen and has good weldability. For heavy-walled process piping intended for subsea sour service, the properties of the root pass are of high importance. For this reason, the effect of using nitrogen in the backing gas was investigated. Test pieces were manually welded with the gas tungsten arc welding (GTAW) process using an ER2209 filler wire. Tensile, bending and hardness testing was carried out and showed acceptable results across all specimens. Higher contents of nitrogen in the backing gas showed more austenite formation and a significant increase in pitting corrosion resistance when compared with pure argon. With Ar + 2 % N2, there was no pitting, but a small weight loss of 1.7 g/m2 was measured. 10 % N2 was required to pass both the corrosion tests ASTM G48 Method A (4 g/m2) and ASTM A923 (1 g/m2). The highest average impact toughness was achieved with pure nitrogen as the backing gas

Simulation study for investment decisions on the EcoBoost camshaft machining line

Design/redesign of manufacturing systems is a complex, risky, and expensive task. Ford Motor Company’s Valencia Engine Plant faces this challenge as it plans to upgrade its machining and assembly lines to introduce the new EcoBoost engines. The research project described in this paper aimed to support the transition process particularly at the camshaft machining line by using simulation modelling techniques. A series of experiments was carried out using the simulation model developed, and recommendations were proposed based on the results of these experiments to support the decision as to where to invest on the line. The outcomes from the research project indicated that investment is required in terms of increasing the capacity of two bottleneck operations through retooling and improving the conveyor routing logic in one key area. Keywords: simulation modelling, closed-loop network, automotive production system