A Technique for generating Feynman Diagrams

We present a simple technique that allows to generate Feynman diagrams for vector models with interactions of order $2n$ and similar models (Gross-Neveu, Thirring model), using a bootstrap equation that uses only the free field value of the energy as an input. The method allows to find the diagrams to, in principle, arbitrarily high order and applies to both energy and correlation functions. It automatically generates the correct symmetry factor (as a function of the number of components of the field) and the correct sign for any diagram in the case of fermion loops. We briefly discuss the possibility of treating QED as a Thirring model with non-local interaction.Comment: 19 pages, LateX, To be published in Z. f. Phys.

Fatigue in seafarers working in the offshore oil and gas re-supply industry: effects of safety climate, psychosocial work environment and shift arrangement

This study examined the influence of safety climate and psychosocial work environment on the reportedfatigue of seafarers working in the offshore oil and gas re-supply industry (n = 402). We found that seafarerswho reported high psychological demands and perceived the organisational-level safety climate negatively,reported significantly more mental fatigue, physical fatigue, and lack of energy. In addition, seafarers whoreported having high levels of job control reported being significantly less mentally fatigued. We also foundsome combined effects of safety climate and shift arrangement. Organisational-level safety climate did notinfluence the levels of physical fatigue in seafarers working on the night shift. On the contrary, seafarersworking during the days reported to be more physically fatigued when they perceived the organisational-levelclimate to be negative compared with the positive. The opposite effect was found for group-level safetyclimate: seafarers working during the nights reported to be more physically fatigued when they perceivedthe group-level climate to be negative compared with the positive. The results from this study point to theimportance of taking into consideration aspects of the psychosocial work environment and safety climate,and their potential impact on fatigue and safety in the maritime organisations

Crystallization of Ge and Si in metal films. II

Heat treatment of evaporated Si in contact with Ag films and Ge in contact with Al films results in the formation of precipitates of the semiconductor in a metal matrix. The structure of these precipitates was studied by transmission electron microscopy and diffraction (TEMD) and MeV 4He ion channeling techniques. TEMD studies showed that the semiconductor precipitates were crystalline in nature. Channeling techniques showed that the crystallites did not have a simple orientation relationship with the underlying single-crystal substrate

Autonomous three-dimensional formation flight for a swarm of unmanned aerial vehicles

This paper investigates the development of a new guidance algorithm for a formation of unmanned aerial vehicles. Using the new approach of bifurcating potential fields, it is shown that a formation of unmanned aerial vehicles can be successfully controlled such that verifiable autonomous patterns are achieved, with a simple parameter switch allowing for transitions between patterns. The key contribution that this paper presents is in the development of a new bounded bifurcating potential field that avoids saturating the vehicle actuators, which is essential for real or safety-critical applications. To demonstrate this, a guidance and control method is developed, based on a six-degreeof-freedom linearized aircraft model, showing that, in simulation, three-dimensional formation flight for a swarm of unmanned aerial vehicles can be achieved