BCIT Citations Collection | BCIT Institutional Repository

BCIT Citations Collection

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Collection of published works from BCIT researchers, faculty, and instructors.

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Dynamic regulation of growing domains for elongating and branching morphogenesis in plants
With their continuous growth, understanding how plant shapes form is fundamentally linked to understanding how growth rates are controlled across different regions of the plant. Much of a plant's architecture is generated in shoots and roots, where fast growth in tips contrasts with slow growth in supporting stalks. Shapes can be determined by where the boundaries between fast- and slow-growing regions are positioned, determining whether tips elongate, branch, or cease to grow. Across plants, there is a diversity in the cell wall chemistry through which growth operates. However, prototypical morphologies, such as tip growth and branching, suggest there are common dynamic constraints in localizing chemical growth catalysts. We have used Turing-type reaction-diffusion mechanisms to model this spatial localization and the resulting growth trajectories, characterizing the chemistry-growth feedback necessary for maintaining tip growth and for inducing branching. The mechanism defining the boundaries between fast- and slow-growing regions not only affects tip shape, it must be able to form new boundaries when the pattern-forming dynamics break symmetry, for instance in the branching of a tip. In previous work, we used an arbitrary concentration threshold to switch between two dynamic regimes of the growth catalyst in order to define growth boundaries. Here, we present a chemical dynamic basis for this threshold, in which feedback between two pattern-forming mechanisms controls the extent of the regions in which fast growth occurs. This provides a general self-contained mechanism for growth control in plant morphogenesis (not relying on external cues) which can account for both simple tip extension and symmetry-breaking branching phenomena., Peer-reviewed article, Published. Received 7 December 2011, Revised 6 March 2012, Accepted 21 March 2012, Available online 28 March 2012.
Dynamic wheelchair seating positions impact cardiovascular function after spinal cord injury
Innovative wheelchairs allow individuals to change position easily for comfort and social situations. While these wheelchairs are beneficial in multiple ways, the effects of position changes on blood pressure might exacerbate hypotension and cerebral hypoperfusion, particularly in those with spinal cord injury (SCI) who can have injury to autonomic nerves that regulate cardiovascular control. Conversely, cardiovascular benefits may be obtained with lowered seating. Here we investigate the effect of moderate changes in wheelchair position on orthostatic cardiovascular and cerebrovascular reflex control.Nineteen individuals with SCI and ten neurologically-intact controls were tested in supine and seated positions (neutral, lowered, and elevated) in the Elevation™ wheelchair. Participants with SCI were stratified into two groups by the severity of injury to cardiovascular autonomic pathways. Beat-to-beat blood pressure, heart rate and middle cerebral artery blood flow velocity (MCAv) were recorded non-invasively.Supine blood pressure and MCAv were reduced in individuals with lesions to autonomic pathways, and declined further with standard seating compared to those with preserved autonomic control. Movement to the elevated position triggered pronounced blood pressure and MCAv falls in those with autonomic lesions, with minimum values significantly reduced compared to the seated and lowered positions. The cumulative duration spent below supine blood pressure was greatest in this group. Lowered seating bolstered blood pressure in those with lesions to autonomic pathways.Integrity of the autonomic nervous system is an important variable that affects cardiovascular responses to orthostatic stress and should be considered when individuals with SCI or autonomic dysfunction are selecting wheelchairs.This work was supported in part by the Heart and Stroke Foundation of British Columbia and the Yukon (V.E.C)., Peer-reviewed article, Published. Received: December 14, 2016 ; Accepted: June 12, 2017 ; Published: June 30, 2017
Dynamic wheeled mobility
31st International Seating Symposium, Nashville, TN, February 26-28, 2015. The prevalence of upper limb pain in full-time manual wheelchair users living with SCI is estimated to be anywhere from 30-70%. For those who rely on an ultralight wheelchair for their day-to-day function, the consequences can be significant and will impact more than just their mobility. Since they were published in 2005, the Clinical Practice Guidelines for Preservation of Upper Limb Function Following Spinal Cord Injury (CPG’s) have served as a valuable evidence-based resource for clinicians and seating/wheeled mobility professionals who work with the SCI population. The recommendations related to wheelchair use are based on extensive research that has examined the effects of the wheelchair’s configuration and the user’s propulsion technique on upper limb function. The recommendations focus on three general areas: Ergonomics, Equipment Selection, and Training., Conference paper, Published.
Early developmental activities and computing proficiency
Proceedings from the 2017 ITiCSE Conference on Working Group Reports. As countries adopt computing education for all pupils from primary school upwards, there are challenging indicators: significant proportions of students who choose to study computing at universities fail the introductory courses, and the evidence for links between formal education outcomes and success in CS is limited. Yet, as we know, some students succeed without prior computing experience. Why is this? Some argue for an innate ability, some for motivation, some for the discrepancies between the expectations of instructors and students, and some -- simply -- for how programming is being taught. All agree that becoming proficient in computing is not easy. Our research takes a novel view on the problem and argues that some of that success is influenced by early childhood experiences outside formal education. In this study, we analyzed over 1300 responses to a multi-institutional and multi-national survey that we developed. The survey captures enjoyment of early developmental activities such as childhood toys, games and pastimes between the ages 0 --- 8 as well as later life experiences with computing. We identify unifying features of the computing experiences in later life, and attempt to link these computing experiences to the childhood activities. The analysis indicates that computing proficiency should be seen from multiple viewpoints, including both skill-level and confidence. Our analysis is the first to show, we believe, that particular early childhood experiences are linked to parts of computing proficiency, namely those related to confidence with problem solving using computing technology. These are essential building blocks for more complex use. We recognize issues in the experimental design that may prevent our data showing a link between early activities and more complex computing skills, and suggest adjustments for future studies. Ultimately, we expect that this line of research will feed in to early years and primary education, and thereby improve computing education for all., Peer reviewed, Conference paper, Published.
An eco-friendly scheme to eliminate silica problems during bamboo biomass fractionation
In this study, an eco-friendly scheme to resolve the silica associated challenges encountered in processing bamboo for biorefineries was evaluated. Bamboo chips were pretreated with sodium hydroxide (NaOH) at low temperature to completely extract silica and partially extract hemicelluloses for follow up conventional kraft pulping or bioethanol production. Silica and hemicellulose in the alkaline pre-extraction liquor (APEL) were sequentially isolated through carbon dioxide (CO2) and ethanol precipitation. High purity (> 99.8%) amorphous silica particles were recovered by carbonating the effluent at 60oC to a pH of 8.2 with CO2. The CO2 adsorption capacity of the APEL was determined to be 7.15g CO2 per liter. After recovering more than 96% of available silica in the APEL, hemicellulose in the CO2-treated liquor was subsequently separated. This study demonstrated the feasibility of pre-extraction and recovery of silica and hemicellulose to alleviate the silica challenges, thereby allowing to expand bamboo as a feedstock for industrial processes., Peer-reviewed article, Published. Manuscript received October 11, 2016; Accepted December 12, 2016.
Ecological footprints and lifestyle archetypes
The global urban transition increasingly positions cities as important influencers in determining sustainability outcomes. Urban sustainability literature tends to focus on the built environment as a solution space for reducing energy and materials demand; however, equally important is the consumption characteristics of the people who occupy the city. While size of dwelling and motor vehicle ownership are partially influenced by urban form, they are also influenced by cultural and socio-economic characteristics. Dietary choices and purchases of consumable goods are almost entirely driven by the latter. Using international field data that document urban ways of living, I develop lifestyle archetypes coupled with ecological footprint analysis to develop consumption benchmarks in the domains of: food, buildings, consumables, transportation, and water that correspond to various levels of demand on nature’s services. I also explore the dimensions of transformation that would be needed in each of these domains for the per capita consumption patterns of urban dwellers to achieve ecological sustainability. The dimensions of transformation needed commensurate with ecological carrying capacity include: a 73% reduction in household energy use, a 96% reduction in motor vehicle ownership, a 78% reduction in per capita vehicle kilometres travelled, and a 79% reduction in air kilometres travelled., Peer-reviewed article, Published. Received: 20 December 2014 ; Revised: 15 March 2015 ; Accepted: 8 April 2015 ; Published: 21 April 2015.
EE13-2 development and benchmarking of a new whole building hygrothermal model
Proceedings of Building Enclosure Science & Technology (BEST2) Conference, Portland, USA, April 12-14, 2010. During design process, building engineers evaluate the performance of various design alternatives in terms of their durability, comfort and indoor air quality, as well as energy efficiency using building envelope, indoor and energy analysis tools, respectively. But, usually the analysis tools are in the form of stand-alone package, where there is no direct link among them but rather simplifying assumptions are made on the other two when designing for one. In this paper, the development and benchmarking of a newly developed whole building hygrothermal model are presented. The model considers the building as a system and accounts for the dynamic heat, air and moisture (HAM) interaction between building envelope components and indoor environmental conditions including HVAC systems, moisture and heat sources. The methodology adopted in this work is to develop and validate two primary models: building envelope and indoor models independently and couple them to form the whole building hygrothermal model. After successful integration of the models, the whole building hygrothermal model is benchmarked against internationally published numerical and experimental test results. The holistic model can be used to assess building enclosures durability, indoor conditions (temperature and relative humidity), occupant comfort, and energy efficiency of a building in an integrated manner., Conference paper, Published.
Effect of alkaline pre-extraction of hemicelluloses and silica on kraft pulping of bamboo (Neosinocalamus affinis Keng)
Commercial bamboo chips were pre-treated with sodium hydroxide (NaOH) solutions to completely extract silica and partially extract hemicelluloses prior to kraft pulping. Reaction temperatures of 80–100 °C, times of 1–5 h, and NaOH charges of 6–18% were explored. With increasing pre-extraction severity, all silica and up to 50% of hemicelluloses in raw chips could be extracted without degrading cellulose and lignin. The chips from select extractions were cooked using the kraft process with varying effective alkali (EA) charges. Pre-extraction resulted in significant improvement in the delignification of chips during subsequent kraft pulping, offering an option to reduce the EA charge or the H-factor. The pulp yield was similar to the control while the drainage resistance of pulp from pre-extracted chips was slightly improved. Physical strength properties of pulps made from pre-extracted chips showed lower tensile index and higher tear index as compared with the control runs. Moreover, silica was no more a problem for chemical recovery and production of high-grade pulp. Extracted silica and hemicelluloses in the alkaline extraction liquor (AEL) can be used as a potential raw material for value-added products., Peer-reviewed article, Published. Received 19 February 2016; Revised 13 June 2016; Accepted 19 June 2016; Available online 15 July 2016.
Effect of attic insulation thickness and solar gain in a mild climate
Attic air ventilation can be influenced by various vent considerations. In addition to vent ratio and location of roof vents, attic insulation thickness can be considered as an influential factor in attic air flow and temperature distribution. Most existing building codes do have a minimum requirement for venting parameters and type and thickness of the insulation used. In this paper, the effect of insulation thickness in attic ventilation rate, attic air temperature and heating and cooling loads in a mild climatic zone is studied. A typical mild climate summer and winter temperatures and solar radiations data are used for 24 hours transient conjugate heat transfer simulations. Results show that solar radiation has significant impact on the amount and the pattern of airflow in attic. An increase in attic insulation yields a decrease in attic ventilation during winter period, but has no effect in summer period for the climate considered. In general, the higher the attic insulation thickness is the lower the building takes advantage of solar gain during winter period, but higher insulation levels tend to be advantageous during summer cooling period., Peer reviewed article, Published. Available online 30 December 2015.
The effect of fiber characteristics on hydrolysis and cellulase accessibility to softwood substrates
The effect of gross fiber characteristics on enzyme accessibility and hydrolysis of Douglas fir kraft pulp substrates was investigated. The average fiber size and coarseness of the substrate had a significant effect on the enzyme adsorption capacity. This was primarily due to the increased specific surface area of small fibers and fines. The observed adsorption capacities were in agreement with the hydrolysis rates and yields because the substrates with the lower average fiber size were hydrolyzed both at a faster rate and more completely. The observed changes in fiber-length distribution and fiber coarseness suggested that the effect of fiber size was most influential during the initial stages of hydrolysis. The small fibers and fines present in heterogeneous, lignocellulosic substrates were hydrolyzed rapidly, yielding a high initial rate of hydrolysis., Peer-reviewed article, Published. Received 27 January 1999; Revised 10 June 1999; Accepted 15 June 1999; Available online 1 November 1999.
Effect of varying surface patterns on antibiotic elution from antibiotic-loaded bone cement
In an effort to improve the antibiotic elution characteristics of the prosthesis of antibiotic-loaded acrylic cement, an in vitro study was conducted. Tobramycin-loaded bone cement blocks of three different surface patterns with different surface area-to-volume ratios were used. The elution of tobramycin over a 2-month period was investigated. There was a gradual decline in the tobramycin elution rate over time. The surface pattern with the increased surface area-to-volume ratio showed a significant increase in the tobramycin elution rate over the first week of the study. The surface pattern with ridges but no change in the surface area-to-volume ratio did not result in a statistically significant increase in the tobramycin elution rate., Peer-reviewed article, Published.
The effects of gene recruitment on the evolvability and robustness of pattern-forming gene networks
Gene recruitment or co-option is defined as the placement of a new gene under a foreign regulatory system. Such re-arrangement of pre-existing regulatory networks can lead to an increase in genomic complexity. This reorganization is recognized as a major driving force in evolution. We simulated the evolution of gene networks by means of the Genetic Algorithms (GA) technique. We used standard GA methods of point mutation and multi-point crossover, as well as our own operators for introducing or withdrawing new genes on the network. The starting point for our computer evolutionary experiments was a 4-gene dynamic model representing the real genetic network controlling segmentation in the fruit fly Drosophila. Model output was fit to experimentally observed gene expression patterns in the early fly embryo. We compared this to output for networks with more and less genes, and with variation in maternal regulatory input. We found that the mutation operator, together with the gene introduction procedure, was sufficient for recruiting new genes into pre-existing networks. Reinforcement of the evolutionary search by crossover operators facilitates this recruitment, but is not necessary. Gene recruitment causes outgrowth of an evolving network, resulting in redundancy, in the sense that the number of genes goes up, as well as the regulatory interactions on the original genes. The recruited genes can have uniform or patterned expressions, many of which recapitulate gene patterns seen in flies, including genes which are not explicitly put in our model. Recruitment of new genes can affect the evolvability of networks (in general, their ability to produce the variation to facilitate adaptive evolution). We see this in particular with a 2-gene subnetwork. To study robustness, we have subjected the networks to experimental levels of variability in maternal regulatory patterns. The majority of networks are not robust to these perturbations. However, a significant subset of the networks do display very high robustness. Within these networks, we find a variety of outcomes, with independent control of different gene expression boundaries. Increase in the number and connectivity of genes (redundancy) does not appear to correlate with robustness. Indeed, removal of recruited genes tends to give a worse fit to data than the original network; new genes are not freely disposable once they acquire functions in the network., Book chapter, Published.
The effects of global climate change on carbonation induced corrosion of reinforced concrete structures
There is nearly unanimous consensus amongst scientists that increasing greenhouse gas emissions, including CO2 generated by human activity, are affecting the Earth‘s climate. Climate change has the potential to overwhelm existing capacities, as well as durability of concrete infrastructure. Carbonation of concrete occurs due to a reaction between atmospheric CO2 and the hydrated phases of concrete, leading to a drop in its pH and the depassivation of embedded rebar. Therefore, increases in carbonation rates of reinforced concrete structures are expected as a result of increased temperatures and CO2 concentrations, with the enhanced risk of carbonation induced corrosion likely affecting the longevity of our concrete infrastructure. This thesis considered the potential consequences of global climate change on our concrete infrastructure, with the objective being to determine if there is an increased risk of deterioration due to carbonation induced corrosion. A unique numerical model was developed to determine carbonation rates in structures, and verified through experimental tests. The model was applied to a numbers of cities in locations throughout the world to determine where structures were most vulnerable. Additionally, a number of other laboratory experiments were carried out to supplement the numerical model and provide insights as to how carbonation progress can be monitored within a structure. Using the model developed, and inputting forecasts for increases in future atmospheric CO2 concentrations and weather conditions, it was shown that for medium quality, non-pozzolonic concrete in geographic areas where carbonation induced corrosion is a concern, global climate change will affect its progress in our concrete infrastructure. We will see much higher ultimate carbonation depths in the long term. The use of non-destructive testing (NDT) methods, and structural health monitoring (SHM) techniques could be invaluable in monitoring the progress of carbonation in a structure, but the data generated by the methods and techniques used must be analyzed carefully before making any conclusions. For the NDT methods and carbonation pH sensors which were evaluated in this study, it was found that ambient test conditions had a major impact on results., Thesis, Published.
The effects of structural cracking on carbonation progress in reinforced concrete
Proceedings of 3rd International Conference on the Durability of Concrete Structures, 17-19 September 2012, Queen’s University Belfast. There is nearly unanimous consensus among scientists that increasing greenhouse gas emissions, including CO2 generated by human activity, are affecting the Earth’s climate. One essential area which will be affected is the durability of concrete infrastructure. Past research indicates that climate change will exacerbate the rate of carbonation of reinforced concrete structures, potentially leading to premature corrosion of embedded rebar. Cracking of the covering concrete could further increase carbonation rates, but the extent of the increase is unknown. The purpose of this study is to investigate the carbonation of cracked concrete under accelerated test conditions, and to numerically model the movement of the carbonation front in cracked concrete using the concept of effective diffusivity. It was found that the presence of a deep structural crack in a concrete specimen greatly increases the rate of carbonation, possibly leading to premature, localized corrosion within the specimen. The effect of cracks is likely to be much greater than the effect of increased temperatures and increased atmospheric CO2 concentrations. As a result, emphasis must be placed on designing durable infrastructure and following proper maintenance practices so that cracks are less likely to form, thereby extending the longevity of the structure in question., Conference paper, Published.
Emotional design
In my teaching and software development practice, I realized that most applications with human-computer interaction do not respond to usersâ emotional needs. The dualism of reason and emotion as two fairly opposite entities that dominated Western philosophy was also reflected in software design. Computing was originally intended to provide applications for military and industrial activities and was primarily associated with cognition and rationality. Today, more and more computer applications interact with users in very complex and sophisticated ways. In human-computer interaction, attention is given to issues of usability and user modeling, but techniques to emotionally engage users or respond to their emotional needs have not been fully developed, even as specialists like Klein, Norman and Picard argued that machines that recognize and express emotions respond better and more appropriately to user interaction (Picard, 1997; Picard & Klein, 2002; Norman, 2004). This study investigated emotion from designersâ perspectives and tentatively concludes that there is little awareness and involvement in emotional design in the IT community. By contrast, participants in this study (36 IT specialists from various fields) strongly supported the idea of emotional design and confirmed the need for methodologies and theoretical models to research emotional design. Based on a review of theory, surveys and interviews, I identified a set of themes for heuristics of emotional design and recommended future research directions. Attention was given to consequences; participants in this study raised issues of manipulation, ethical responsibilities of designers, and the need for regulations, and recommended that emotional design should carry standard ethical guidelines for games and any other applications. The research design utilized a mixed QUAN-qual methodological model proposed by Creswell (2003) and Gay, Mills, and Airasian (2006), which was modified to equally emphasize both quantitative and qualitative stages. An instrument in the form of a questionnaire was designed, tested and piloted in this study and will be improved and used in future research., Published., Peer reviewed, Thesis/Dissertation
Emotional design
Proceedings from the First Biannual Conference on Technological Learning and Thinking: Culture, Design, Sustainability, Human Ingenuity held in Vancouver, BC, Canada, 2010., Not peer reviewed, Conference paper

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