Case-study evaluations of the acoustical designs of renovated university classrooms

The acoustical characteristics of 14 university classrooms at the University of British Columbia were measured before and after renovation—seven of these are discussed in detail here. From these measurements, and theoretical considerations, values of quantities used to assess each classroom configuration were predicted, and used to evaluate renovation quality. Information on each renovation was determined with the help of the university campus-planning office and/or the project acoustical consultant. These were related to the evaluation results in order to determine the relationship between design and acoustical quality. The criteria focused on the quality of verbal communication in the classrooms. Room-average Speech Intelligibility (SI) and its physical correlate, Speech Transmission Index (STI), were used to quantify verbal-communication quality. A simplified STI-calculation procedure was applied. The results indicate that some renovations were beneficial, others were not. Verbal-communication quality varied from ‘poor’ to ‘good’. The effect of a renovation depends on a complex interplay between changes in the reverberation and changes in the signal-to-noise level difference, as affected by sound absorption and the source outputs. Renovations which reduce noise are beneficial unless signal-to-noise level differences remain optimal. Renovations often put too much emphasis on adding sound absorption to control reverberation, at the expense of lower speech levels, particularly at the backs of classrooms. The absorption and noise contributed by room occupants has apparently often been neglected.     

Control of the block copolymer morphology in templated epoxy thermosets

It has been found that by the addition of low concentrations of an amphiphilic block copolymer to an epoxy resin, novel disordered morphologies can be formed and preserved through curing. This article will focus on characterizing the influence of the block copolymer and casting solvent on the templated morphology achieved in the thermoset sample. The ultimate goal of this work is to determine the parameters that would control the microphase morphology produced. Epoxy resins blended with a series of amphiphilic block copolymers based on hydrogenated polyisoprene (polyethylene-alt-propylene or PEP) and polyethylene oxide (PEO), specifically, were investigated. In this article, the cure-induced order–order phase transition from the spherical to wormlike micelle morphology will also be discussed. It is proposed that the formation of the wormlike micelle structure from the spherical micelle structure is similar to the phase transition behavior that occurs in dilute block copolymer solutions as a function of the influence of the solvent on micelle morphology. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3338–3348, 2007     

Reorientational relaxation and rotational–translational coupling in water clusters in a d.c. external electric field

Molecular dynamics simulations have been carried out for small water clusters (N=16, 32, 64) in a d.c. electric field at T=200 K. It was shown that for relatively weak fields, there was a significant decrease of reorientational and structural relaxation times for all cluster sizes examined. Regarding the molecular reorientational motions, in the strong field regime, a decoupling of tumbling and spinning librations was observed. Reorientational relaxation times of the dipole and vector joining the two hydrogen atoms were found to follow different relaxation laws, with the former decreasing and the latter increasing with electric field increase. These trends were qualitatively explained by invoking the Debye model with field-dependent friction for dipole librations and the symmetric double-well for spinning rotations on a plane perpendicular to the field axis. Finally, the interdependence of the reorientation on the translational modes of the cluster was indicated, with the translationally slow molecules being rotationally slow as well and vice versa.     

String structures and the path fibration of a group

We use the realisation of the universal bundle for the loop group as the path fibration of the group to investigate the string class, that is the obstruction to a loop group bundle lifting to a Kac-Moody group bundle. In the case that the loop group bundle is constructed by taking loops into a principal bundle we show that the classifying map is the holonomy around loops and give an explicit formula for the string class relating it to the Pontrjangin class of the principal bunble.     

The design, synthesis, and characterization of a PAMAM-based triple helical collagen mimetic dendrimer

The synthesis and characterization of a collagen mimetic dendrimer composed of the Gly-Pro-Nleu sequence is described. The dendrimer is built on a ‘first generation’ poly(amidoamine) core and is synthesized in 38% yield. This dendrimer exhibits a melting temperature of 25 °C, which is in between previously studied analogous molecules of identical sequence and length.     

Self-assembly of a linear mesoscale tetramer with electrical connectivity

Capillary interaction-based self-assembly of block-shaped mesoscale components into an electrically interconnected 1-D tetramer is reported. Low melting point solder droplets, selectively patterned on the faces of the blocks, were employed to drive the sequential alignment, registration, linking and electrical interconnection of each block. The solder patterns were designed so that successful assembly would only occur when the solder patterns on one block face were correctly aligned with those on the face of an adjacent block. For assembly, the blocks were agitated in a flask containing KBr solution. At 60 °C the solder was molten, and collisions between blocks enabled the solder menisci to easily interact. To minimize interfacial free energy, the menisci coalesced and quickly drove the interacting blocks to form a stable, registered and aligned assembly. When agitation was terminated and the solution cooled, the self-aligned, linear tetrameric arrangement of blocks was permanently captured by solder solidification, a process that provided good mechanical bonding and electrical interconnection between each block. PACS 81.16.Dn; 68.03.Cd; 85.40.-e     

The proportional hazards regression model with staggered entries: A strong martingale approach

The proportional hazards regression model, when subjects enter the study in a staggered fashion, is studied. A strong martingale approach is used to model the two-time parameter counting processes. It is shown that well-known univariate results such as weak convergence and martingale inequalities can be extended to this two-dimensional model. Strong martingale theory is also used to prove weight convergence of a general weighted goodness-of-fit process and its weighted bootstrap counterpart.