Hyperventilation and submarine escape

The Royal Navy have demonstrated in two sea trials that it is possible for men to make successful escapes from submarines at depths of about 600 ft. However, the outcomes suggest this depth is close to the limit of safe escape under ideal conditions and might be well beyond it in real circumstances. The problem lies in the substantial accumulation of nitrogen which occurs in nervous tissue during all but the last few seconds of the brief escape procedure. As the surface of the sea is approached the nitrogen may evolve destructively as bubbles. This thesis explores the idea that hyperventilation prior to escape might reduce the risk of bubble formation. Hyperventilation lowers the partial pressure of CO2 in arterial blood. This is known to constrict cerebrospinal arteries and arterioles and so should restrict the build up of dissolved nitrogen in central nervous tissue. Preliminary experiments by others have indicated that human volunteers can complete the escape procedure successfully after hyperventilating to a PACO2 of 20 mmHg or so. This degree of hyperventilation should halve the inflow of nitrogen

Study of new flight test techniques

The modification and testing of a small electromechanical vibrator are described. The vibrator was designed for the flutter testing of aircraft wings and was built to specifications that make it compatible with the X-29 experimental aircraft. The device uses alternating electromagnetic forces to move a magnetic mass and produce vibration. Its unconventional way of producing vibration avoids the need for complex mechanisms and makes efficient use of space and weight

Field-theoretical approach to a dense polymer with an ideal binary mixture of clustering centers

We propose a field-theoretical approach to a polymer system immersed in an ideal mixture of clustering centers. The system contains several species of these clustering centers with different functionality, each of which connects a fixed number segments of the chain to each other. The field-theory is solved using the saddle point approximation and evaluated for dense polymer melts using the Random Phase Approximation. We find a short-ranged effective inter-segment interaction with strength dependent on the average segment density and discuss the structure factor within this approximation. We also determine the fractions of linkers of the different functionalities.Comment: 27 pages, 9 figures, accepted on Phys. Rev.

Elasticity of highly cross-linked random networks

Starting from a microscopic model of randomly cross-linked particles with quenched disorder, we calculate the Laudau-Wilson free energy S for arbitrary cross-link densities. Considering pure shear deformations, S takes the form of the elastic energy of an isotropic amorphous solid state, from which the shear modulus can be identified. It is found to be an universal quantity, not depending on any microscopic length-scales of the model.Comment: 6 pages, 5 figure

Tension perpendicular to grain strength of wood, Laminated Veneer Lumber (LVL), and Cross-Banded LVL (LVL-C)

Recent experimental tests carried out on structural timber members have highlighted the importance of tension perpendicular to grain strength, particularly in beams with holes and notches, in connection regions, in curved beams, and in post-tensioned timber frames. Innovative engineered wood products such as Cross Banded Laminated Veneer Lumber (LVL-C) have been introduced into the market specifically to improve the perpendicular to grain properties of normal Laminated Veneer Lumber (LVL). This paper reports on tests that were performed at the University of Canterbury using specimens of sawn timber Radiata Pine, LVL and LVL-C. The perpendicular to grain tension strengths of LVL was generally lower than those for sawn timber, but the LVL-C showed a significantly improved strength. The paper also compares the experimental results with strengths predicted using both coupled elastic Finite Element Method (FEM) and Linear Elastic Fracture Mechanics (LEFM) models. These models were found to predict the average strength with reasonable accuracy. © 2011 Taylor & Francis Group, London