Understanding the wage patterns of Canadian less skilled workers: the role of implicit contracts

We examine the wage patterns of Canadian less skilled male workers over the last quarter century by organizing workers into job entry cohorts. We find entry wages for successive cohorts declined until 1997, and then began to recover. Wage profiles steepened for cohorts entering after 1997, but not for cohorts entering in the 1980s - a period when start wages were relatively high. We argue that these patterns are consistent with a model of implicit contracts with recontracting in which a worker's current wage is determined by the best labour market conditions experienced during the current job spell.

Accurate modeling of parallel scientific computations

Scientific codes are usually parallelized by partitioning a grid among processors. To achieve top performance it is necessary to partition the grid so as to balance workload and minimize communication/synchronization costs. This problem is particularly acute when the grid is irregular, changes over the course of the computation, and is not known until load time. Critical mapping and remapping decisions rest on the ability to accurately predict performance, given a description of a grid and its partition. This paper discusses one approach to this problem, and illustrates its use on a one-dimensional fluids code. The models constructed are shown to be accurate, and are used to find optimal remapping schedules

Fabrication and Characterization of Silicon Carbide Epoxy Composites

Nanoscale fillers can significantly enhance the performance of composites by increasing the extent of filler-to-matrix interaction. Thus far, the embedding of nanomaterials into composites has been achieved, but the directional arrangement has proved to be a challenging task. Even with advances in in-situ and shear stress induced orientation, these methods are both difficult to control and unreliable. Therefore, the fabrication of nanomaterials with an ability to orient along a magnetic field is a promising pathway to create highly controllable composite systems with precisely designed characteristics. To this end, the goal of this dissertation is to develop magnetically active nanoscale whiskers and study the effect of the whiskers orientation in a polymer matrix on the nanocomposite\u27s behavior. Namely, we report the surface modification of silicon carbide whiskers (SiCWs) with magnetic nanoparticles and fabrication of SiC/epoxy composite materials. The magnetic nanoparticles attachment to the SiCWs was accomplished using polyelectrolyte polymer-to-polymer complexation. The “grafting to†and adsorption techniques were used to attach the polyelectrolytes to the surface of the SiCWs and magnetic nanoparticles. The anchored polyelectrolytes were polyacrylic acid (PAA) and poly(2-vinylpyridine) (P2VP). Next, the SiC/epoxy composites incorporating randomly oriented and magnetically oriented whiskers were fabricated. The formation of the composite was studied to determine the influence of the whiskers\u27 surface composition on the epoxy curing reaction. After curing, the composites\u27 thermal and thermo-mechanical properties were studied. These properties were related to the dispersion and orientation of the fillers in the composite samples. The obtained results indicated that the thermal and thermo-mechanical properties could be improved by orienting magnetically-active SiCWs inside the matrix. Silanization, “grafting toâ€, adsorption, and complexation were used to modify the surface of SiCWs to further investigate the epoxy nanocomposite system. The process of composites formation was studied to evaluate the effects of the surface modification on the epoxy curing reaction. The obtained composites were tested and analyzed to assess their thermal and thermo-mechanical properties. These properties were related to the dispersion and surface chemical composition of the fillers in the nanocomposites. It was determined that magnetically modified SiCWs have lower ability for interfacial stress transfer in the composite systems under consideration. The final portion of this work was focused on reinforcing the magnetic layer of the SiCWs. This was accomplished by structurally toughening the magnetic layer with poly(glycidyl methacrylate) (PGMA) layer. As a result, the thermal and mechanical properties of the magnetic composite system were improved significantly

Lossless compression with latent variable models

We develop a simple and elegant method for lossless compression using latent variable models, which we call `bits back with asymmetric numeral systems' (BB-ANS). The method involves interleaving encode and decode steps, and achieves an optimal rate when compressing batches of data. We demonstrate it rstly on the MNIST test set, showing that state-of-the-art lossless compression is possible using a small variational autoencoder (VAE) model. We then make use of a novel empirical insight, that fully convolutional generative models, trained on small images, are able to generalize to images of arbitrary size, and extend BB-ANS to hierarchical latent variable models, enabling state-of-the-art lossless compression of full-size colour images from the ImageNet dataset. We describe `Craystack', a modular software framework which we have developed for rapid prototyping of compression using deep generative models

Corytophanes cristatus

Number of Pages: 6Integrative BiologyGeological Science

Following the relaxation dynamics of photoexcited aniline in the 273-266 nm region using time-resolved photoelectron imaging

Scanning tunnelling microscopy (STM) and Auger electron spectroscopy (AES) have been used to investigate the growth morphology of ultra-thin Pb films on the Ni3Al(111) face at room temperature. A previous study [K. Miśków and A. Krupski Appl Surf Sci 273, 2013, 554] using low-energy electron diffraction (LEED) and real time Auger intensity recording has demonstrated that an initial two-dimensional growth of the first Pb monolayer thick ‘wetting layer’ takes place. With further deposition and for T = 300 K, flat three atomic-layer-high islands are grown. Above 350 K, the Stranski–Krastanov growth mode was observed. In the current study, the analysis of STM measurements indicate and confirm that for coverage θ = 1.0 ML two-dimensional growth of the first Pb monolayer took place. Above θ > 1.0 ML, a three-dimensional growth of the Pb islands was observed with a strongly preferred atomic-scale ‘magic height (N),’ hexagonal shape and flat-tops. At coverage θ = 3.5 ML, only islands containing N = 3, 5, 7 and 11 atomic layers of Pb are observed. At the higher coverage θ = 5.5 ML, three types of regular hexagonal islands with side lengths of 25, 30 and 45 nm are observed. Furthermore, three different island adsorption configurations rotated by 10° ± 1° and 30° ± 6° with respect to each other were observed. After an annealing at T = 400 K of 5.5 ML of lead deposited at RT on the Ni3Al(111) the morphology of the surface changes. Post-anneal, islands of Pb are observed above the ‘wetting layer’ with an estimated average size and diameter of 768 ± 291 nm2 and 38.17 ± 6.56 nm and constant uniform height of two atomic layers (N = 2)