Procedural Methods for Urban Modeling

Simulation of our man-made environment, especially cities, is becoming an increasingly important research problem in computer graphics. This special issue captures a good snapshot of work in this emerging area.     

Exploring Particle Density Effects on Partial Mobility of Steelhead Spawning Gravels

Yellowbank Creek is a small stream in coastal central California being assessed for salmonid habitat limiting factors and restoration potential. Yellowbank flows through low‐density marine mudstone bedrock, which is the gravel source for the stream. To assess the potential effects of the low‐density substrate on spawning gravels, a tracer stone study comparing the incipient motion of low‐density mudstone particles and typical density granitic particles was used to populate a logistic regression particle entrainment model. A model comparison approach was used to test the strength of the model. Results demonstrate partial mobility of both mudstone and granitic particles under boundary shear conditions ranging from 6.9 to 42.2 N m^‐2. The modelling results quantify the strong negative correlation between particle entrainment and particle density. Mudstone gravel was three times more likely to be entrained than granitic gravel, within the context of the experimental conditions. The effect of density difference on partial mobility was greater in smaller grain size fractions. This work has implications for salmonid spawning success in atypical geologic settings and may assist in prioritization of restoration efforts. Copyright © 2013 John Wiley & Sons, Ltd.     

Not Just “A Roof over Your Head”: The Meaning of Healthy Housing for People Living with HIV

The literature has identified housing as a fundamental unmet need for people living with HIV; yet there has been little qualitative evidence exploring housing and HIV, particularly from a Canadian context. This paper focuses on our qualitative analyses of the housing experiences of 48 HIV-positive people living in Ontario. Findings from our interviews illustrate healthy housing as a dynamic interconnection between health, housing and other social factors that are influential to the health and well-being of people with HIV. Four salient themes have emerged from our qualitative findings: the interplay between healthy housing and economic security; the relationship between HIV, health and housing precariousness; the interconnection between housing, HIV, safety, stigma, social isolation and social exclusion; and the meaning of healthy housing for people living with HIV. These findings re-emphasize the importance of housing policies that consider housing as more than just a roof over one’s head, but also as something that supports the physical, mental, emotional and social well-being of people living with HIV.     

Recent developments in hot plate welding of thermoplastics

This paper considers the hot plate welding process applied to three injection molded thermoplastic materials: polypropylene, high impact polystyrene, and poly(phenylene oxide). Weld quality was assessed by tensile testing. The process was found to be suitable for all three materials, although tolerance to variations in process parameters varied. The parameters in the heating phase, i.e., hot plate temperature and time, were the most important for achieving good welds, whereas parameter variations in the consolidation phase were relatively unimportant.     

Analysis of dependent events and multiple unavailabilities with particular reference to common-cause failures

Historically the concern of reliability engineers in the aircraft, nuclear and chemical industries when dealing with dependent failures in high integrity systems has been with common mode or common cause failures. Starting from this perspective the paper considers dependent events, failure definition and classification schemes. Recently these schemes have explicitly distinguished different types of multi-unavailabilities and dependent events. The CSNI and EPRI sponsored data analyses are reviewed. CCF modelling and defenses are discussed and the limitations imposed by data are shown to lead to a possible requirement to consider a structured model that enables the engineer to consider various factors explicitly which could affect the specific system being assessed. This enables judgement to be used in an explicit way in evaluating common cause failures.     

Direct measurement of the Cu oxidation number of cuprate superconductor ceramics

The Cu oxidation number in YBa₂Cu₃O₇ has been measured directly by soft X-ray fluorescent spectroscopy both at room temperature and at liquid N₂ temperature. The measurements are based on a calibration curve from different Ba-O compounds. The effect of changes in oxidation number above and below the transition temperature and its role in highT _c superconductivity are discussed.