Environmental legislation as a driver of design

and other research output

Reconstructing the global topology of the universe from the cosmic microwave background

If the universe is multiply-connected and sufficiently small, then the last scattering surface wraps around the universe and intersects itself. Each circle of intersection appears as two distinct circles on the microwave sky. The present article shows how to use the matched circles to explicitly reconstruct the global topology of space.Comment: 6 pages, 2 figures, IOP format. To be published in the proceedings of the Cleveland Cosmology and Topology Workshop 17-19 Oct 1997. Submitted to Class. Quant. Gra

Circles in the Sky: Finding Topology with the Microwave Background Radiation

If the universe is finite and smaller than the distance to the surface of last scatter, then the signature of the topology of the universe is writ large on the microwave background sky. We show that the microwave background will be identified at the intersections of the surface of last scattering as seen by different ``copies'' of the observer. Since the surface of last scattering is a two-sphere, these intersections will be circles, regardless of the background geometry or topology. We therefore propose a statistic that is sensitive to all small, locally homogeneous topologies. Here, small means that the distance to the surface of last scatter is smaller than the ``topology scale'' of the universe.Comment: 14 pages, 10 figures, IOP format. This paper is a direct descendant of gr-qc/9602039. To appear in a special proceedings issue of Class. Quant. Grav. covering the Cleveland Topology & Cosmology Worksho

A. C. Power Losses in MOV Surge Arrestors

It was the objective of this study to measure power losses occurring in MOV surge arrestors as they were subjected to various voltage Excitations. In particular, power losses were observed in two MOV devices as sinusoidal voltages of different magnitudes were applied, at various frequencies in the range of typical power frequencies and common harmonics. Power losses were also observed in an MOV device for applied voltages consisting of the sum of 60 Hertz sinusoids and a single harmonic. The measurement procedure consisted of obtaining digital records representing the waveforms of voltage across and current through the MOV device during operation; power was calculated as the mean of the product of these digitally represented waveforms; This report contains a detailed description of the implementation of this procedure, as well as a discussion of some of its limitations when making measurements on highly reactive devices. Experimental results indicate that power losses in the MOV devices studied were primarily dependent upon frequency of operation, and peak amplitude of applied voltage. The results indicate that 60 Hertz specifications given for a particular device do not, in general, apply for other frequencies or non-sinusoidal excitation

Description of the fluctuating colloid-polymer interface

To describe the full spectrum of surface fluctuations of the interface between phase-separated colloid-polymer mixtures from low scattering vector q (classical capillary wave theory) to high q (bulk-like fluctuations), one must take account of the interface's bending rigidity. We find that the bending rigidity is negative and that on approach to the critical point it vanishes proportionally to the interfacial tension. Both features are in agreement with Monte Carlo simulations.Comment: 5 pages, 3 figures, 1 table. Accepted for publication in Phys. Rev. Let

Bostonia: The Boston University Alumni Magazine. Volume 29

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs

Running-in and micropitting behaviour of steel surfaces under mixed lubrication conditions

The paper investigates the running-in of hardened steel surfaces under mixed lubrication conditions. Pairs of surfaces of both equal and differing hardness were loaded together under rolling/sliding conditions in a twin-disk rig, and the evolution of surface topography was investigated using in-situ profilometry. Evaluation of roughness parameters, height distributions and profile relocation showed that the running-in of these surfaces is a rapid process where the most prominent asperity tips undergo plastic deformation during the initial loading cycles. Finally, the pair of equal hardness disks, following further running in a separate series of experiments, was found to suffer from micro-pitting. This micropitting predominantly occurred along the tips of prominent asperities, and the potential link between running-in and surface failure is discussed

Skylab floating ice experiment

The author has identified the following significant results. Coupling of the aircraft data with the ground truth observations proved to be highly successful with interesting results being obtained with IR and SLAR passive microwave techniques, and standard photography. Of particular interest were the results of the PMIS system which operated at 10.69 GHz with both vertical and horizontal polarizations. This was the first time that dual polarized images were obtained from floating ice. In both sea and lake ice, it was possible to distinguish a wide variety of thin ice types because of their large differences in brightness temperatures. It was found that the higher brightness temperature was invariably obtained in the vertically polarized mode, and as the age of the ice increases the brightness temperature increases in both polarizations. Associated with this change in age, the difference in temperature was observed as the different polarizations decreased. It appears that the horizontally polarized data is the most sensitive to variations in ice type for both fresh water and sea ice. The study also showed the great amount of information on ice surface roughness and deformation patterns that can be obtained from X-band SLAR observations

Super-roughening as a disorder-dominated flat phase

We study the phenomenon of super-roughening found on surfaces growing on disordered substrates. We consider a one-dimensional version of the problem for which the pure, ordered model exhibits a roughening phase transition. Extensive numerical simulations combined with analytical approximations indicate that super-roughening is a regime of asymptotically flat surfaces with non-trivial, rough short-scale features arising from the competition between surface tension and disorder. Based on this evidence and on previous simulations of the two-dimensional Random sine-Gordon model [Sanchez et al., Phys. Rev. E 62, 3219 (2000)], we argue that this scenario is general and explains equally well the hitherto poorly understood two-dimensional case.Comment: 7 pages, 4 figures. Accepted for publication in Europhysics Letter