Ryerson University

About: Ryerson University is a education organization based out in Toronto, Ontario, Canada. It is known for research contribution in the topics: Population & Poison control. The organization has 7671 authors who have published 20164 publications receiving 394976 citations. The organization is also known as: Ryerson Polytechnical Institute & Ryerson Institute of Technology.

Frost resistance and microstructure of Engineered Cementitious Composites: Influence of fly ash and micro poly-vinyl-alcohol fiber

Abstract: One of the most damaging environmental conditions to concrete structure is cyclic freezing and thawing This paper discusses the influence of the high volumes of fly ash (FA) and micro poly-vinyl-alcohol (PVA) fibers on the cyclic freeze–thaw resistance and microstructure of the Engineered Cementitious Composites (ECC) ECC mixtures with two different FA–cement (FA/C) ratios (12 and 22 by weight), and at constant water-cementitious materials (fly ash and cement) ratio of 027 are prepared To compare the behavior of ECC with ECC matrix, all of the preceding properties are also investigated for ECC matrix mixtures of same composition without PVA fiber For frost resistance, mixtures are exposed to the freeze and thaw cycles up to 300 cycles in accordance with ASTM C666, Procedure A Experimental tests consist of measuring the residual mechanical properties (flexural strength, mid-span beam deflection and flexural stress – deflection curve), ultrasonic pulse velocity and mass loss The roles of PVA fibers and FA are discussed through the analysis of microstructure and fiber–matrix interactions as function of frost exposure The microstructural characterization by measuring pore size distributions is examined before and after exposure to frost deterioration by using mercury intrusion porosimetry (MIP) The air-void characteristics of mixtures are also studied using linear transverse method Test results confirm that both ECC mixtures with high volumes of FA remain durable, and show a tensile strain capacity of more than 2% even after 300 freezing and thawing cycles On the other hand, before completing 300 freezing and thawing cycles, matrix (ECC without fiber) specimens have severely deteriorated, requiring removal from the freeze–thaw machine Therefore, results indicate that the addition of micro PVA fiber to the ECC matrix substantially improved the frost resistance The results of freeze–thaw tests also indicated that the reduction of residual physical and mechanical properties with increasing number of freeze–thaw cycles is relatively more for ECC mixture with FA/C ratio of 22 than for ECC mixture with FA/C ratio of 12

The Limits and Opportunities of Networks: Municipalities and Canadian Climate Change Policy

Abstract: Research on climate change policy and politics has become increasingly focused on the actions and influence of subnational governments. In North America, this attention has been particularly focused on why subnational governments have taken action in the absence of national leadership, what effect action might have on future national climate policy, and whether the collective action of networks of municipal governments are reshaping and challenging the character of national and global climate governance. This paper examines Canadian municipal climate in light of the absence of a comprehensive and effective climate national strategy. The paper considers various reasons why local governments in Canada have not been central players in national plans, and why their actions have not been more influential nationally. The paper argues that the potential influence of Canadian municipalities on national climate policy is weak, given the loose nature of the network and the long-held structural view that municipalities are not significant units of political analysis in national political and policy debates. The paper concludes by considering the constraints and opportunities of subnational climate networks and municipal network analysis.

Granular computing, computational intelligence, and the analysis of non-geometric input spaces

Abstract: Data granulation emerged as an important paradigm in modeling and computing with uncertainty, exploiting information granules as the main mathematical constructs involved in the context of granular computing. In this paper, we comment on the importance of data granulation in computational intelligence methods. Toward this aim, we discuss also the peculiar aspects related to the analysis of non-geometric patterns, which have recently attracted considerable attention by researchers. As a conclusion, we elaborate over the fundamental, conceptual problems underlying the process of data granulation, which drive the quest for a sound theory of granular computing.

A new method for 3D individual tree extraction using multispectral airborne LiDAR point clouds

Abstract: Characterization of individual trees is essential for many applications in forest management and ecology. Previous studies relied on single tree detection from monochromatic wavelength airborne laser scanning (ALS) systems and they focused on the use of the geometric spatial information of the point clouds (i.e., X, Y, and Z coordinates). However, there is quite often a difficulty dealing with clumped trees when only the geometric spatial information is considered. The emergence of multispectral LiDAR sensors provides a new solution for individual tree structure acquisition. The aim of this paper is to investigate the performance of multispectral ALS data for delineating individual trees which are challenging by using the monochromatic wavelength ALS system. The proposed workflow utilizes the mean shift segmentation method on different feature spaces for crown isolation. In addition, both spatial domain and multispectral domain are used to refine the under-segmentation crown segments. Ten plots (2 sets of different structural complexity) located in the dense coniferous forest area in Tobermory, Ontario, Canada are selected as experiment data. Results show that the developed method correctly detects 88% and 82% of the dominant trees with and without multispectral information, respectively. Compared with segmentation using geometric spatial information solely, the main improvements are achieved for clumped tree segment with the distinguished multispectral features. This study demonstrates that multispectral airborne laser scanning data is more capable for individual tree delineation than monochromatic wavelength laser scanning data in dealing with forests with clumped crowns in dense forests.

Tensile properties and strain-hardening behavior of double-sided arc welded and friction stir welded AZ31B magnesium alloy

Abstract: Microstructures, tensile properties and work hardening behavior of double-sided arc welded (DSAWed) and friction stir welded (FSWed) AZ31B-H24 magnesium alloy sheet were studied at different strain rates. While the yield strength was higher, both the ultimate tensile strength and ductility were lower in the FSWed samples than in the DSAWed samples due to welding defects present at the bottom surface in the FSWed samples. Strain-hardening exponents were evaluated using the Hollomon relationship, the Ludwik equation and a modified equation. After welding, the strain-hardening exponents were nearly twice that of the base metal. The DSAWed samples exhibited stronger strain-hardening capacity due to the larger grain size coupled with the divorced eutectic structure containing -Mg17Al12 particles in the fusion zone, compared to the FSWed samples and base metal. Kocks-Mecking type plots were used to show strain-hardening stages. Stage III hardening occurred after yielding in both the base metal and the welded samples. At lower strains a higher strain-hardening rate was observed in the base metal, but it decreased rapidly with increasing net flow stress. At higher strains the strain-hardening rate of the welded samples became higher, because the recrystallized grains in the FSWed and the larger re-solidified grains coupled with particles in the DSAWed provided more space to accommodate dislocation multiplication during plastic deformation. The strain-rate sensitivity evaluated via Lindholm's approach was observed to be higher in the base metal than in the welded samples. © 2010 Elsevier B.V. All rights reserved.