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BCIT Citations Collection

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Modelling cryptographic protocols in a theory of action
Proceedings of the Ninth International Symposium on Logical Formalizations of Commonsense Reasoning, Toronto, ON, June 1-3, 2009. This paper proposes a framework for analysing cryptographic protocols by expressing message passing and possible attacks as a situation calculus theory. While cryptographic protocols are usually quite short, they are nonetheless notoriously difficult to analyse, and are subject to subtle and nonintuitive attacks. Our thesis is that in previous approaches for expressing protocols, underlying domain assumptions and capabilities of agents are left implicit. We propose a declarative specification of such assumptions and capabilities in the situation calculus. A protocol is then compiled into a sequence of actions to be executed by the principals. A successful attack is an executable plan by an intruder that compromises the stated goal of the plan. We argue that not only is a full declarative specification necessary, it is also much more flexible than previous approaches, permitting among other things interleaved runs of different protocols and participants with varying abilities., Conference paper, Published.
Modelling the effects of structural cracking on carbonation front advance into concrete
Concrete structures are almost certain to contain cracks due to different physiochemical mechanisms. The formation of cracks is sure to affect its durability by altering ion and fluid transport properties. This includes the incursion of CO2 into the structure. There presently exists no consensus on how to model the effects of structural cracking on carbonation progress within concrete structures. This paper first examines the concept of effective diffusion based on simultaneous diffusion of CO2 through sound and cracked concrete and then considers a series diffusion concept where CO2 diffuses first into the crack, and then outwards into the sound concrete. It is concluded that the effective diffusion concept is not valid for structurally cracked concrete. Instead, research efforts should be concentrated on developing a two–phase series diffusion model., Peer-reviewed article, Published.
Moisture response of sheathing board in conventional and rain-screen wall systems with shiplap cladding
Building enclosures are subjected to a random climatic loading on the exterior surface and a relatively stable indoor condition on the interior. These loadings result in a transport of heat, air, and moisture across the building enclosure. In this paper, the drying and wetting of sheathing board in two exterior walls, more specifically 2×6 in.2 wood-frame conventional (no strapping between sheathing membrane and cladding) and a rain-screen wall system (with vertical strapping), are investigated through an experimental field study. The experiment is carried out at British Columbia Institute of Technology field exposure test facility, where the test walls are exposed to the coastal climate (Vancouver weather) on the exterior and controlled indoor temperature and relative humidity conditions in the interior. The field experimental results indicate significant moisture accumulation on the exterior sheathing boards (plywood) during the Winter period. During the 9-month monitoring period from March 13 to Dec. 6, 2009, the plywood underwent a process of drying and wetting. In both the conventional and rain-screen wall systems, the plywood dried to a comparable moisture level during the Summer before the wetting process started. For the wall systems considered in this study, the plywood in the rain-screen wall has a tendency of faster drying and wetting in the Spring and Fall seasons, respectively, in comparison to the plywood in the conventional wall, which is attributed to the presence of an air gap in the rain-screen wall between the sheathing membrane and the cladding. A similar trend is observed during the monitoring period from December 7 to June 15, 2010., Peer-reviewed article, Published. Manuscript received January 14, 2010; accepted for publication August 14, 2010; published online October 2010.
Molecular targets for therapeutic intervention after spinal cord injury
In an effort to develop therapies for promoting neurological recovery after spinal cord injury, much work has been done to identify the cellular and molecular factors that control axonal regeneration within the injured central nervous system. This review summarizes the current understanding of a number of the elements within the spinal cord environment that inhibit axonal growth and outlines the factors that influence the neuron’s ability to regenerate its axon after injury. Recent insights in these areas have identified important molecular pathways that are potential targets for therapeutic intervention, raising hope for victims of spinal cord injury., Peer-reviewed article, Published.
Motivating high school girls to study computer science
This research study aims to identify design strategies, instructional models and technological tools (e.g., educational games) that can be used to motivate high school girls to pursue computer science (CS) education. Part of this study, an educational game CodeBlock intended to teach basic programming, was designed and implemented for HoloLens devices. This study evaluates to what extent participating in a coding workshop consisting of a set of coding exercises and the CodeBlock game play could increase the interest of high school girls in CS. The workshop is conducted by undergraduate students who were involved in the design and implementation of the game, which has an additional benefit of exposing young girls to technologies implemented by post-secondary students, thus increasing the chances they will pursue post-secondary education in CS related fields., Not peer reviewed, Conference proceedings
The need for an accurate indoor humidity model for building envelope performance analysis
Proceedings of the Fourth International Building Physics Conference: Energy Efficiency and New Approaches: 15 June 2009, Istanbul, Turkey. The performance of a building envelope component is usually assessed based on the moisture analysis of individual components (such as cladding, sheathing board and/or drywall) for their drying potentials and likelihood of occurrence of problems associated with high moisture accumulation. In the current building envelope simulation practice, the indoor and outdoor boundary conditions are predefined in the context of the local weather data. The indoor boundary conditions are usually assumed to be constant throughout the simulation period, or two sets of values for the summer and winter periods are assumed. Although the outdoor boundary condition (weather data) is independent of the hygrothermal condition of the envelope, the indoor condition is highly influenced by the building enclosure and occupants? activities. Consequently, simplistic assumptions of indoor humidity profiles, which ignore the dynamic coupling of the indoor environment and building enclosure and represented with a set of empirical values, may lead to inaccurate conclusion about the moisture performance of the building enclosure. In this paper, the effects of indoor humidity profiles that are assumed during moisture performance evaluation of exterior building envelope component are analyzed. The indoor humidity profiles, which are considered in the study, are based on measured and simulated data of a real house. Indoor humidity models including a whole building hygrothermal model are used to generate four indoor humidity profiles. The hygrothermal dynamic responses of the building envelope component with respect to the various cases of indoor humidity assumptions are simulated and analyzed. The simulation results suggest that it is important to have more accurate indoor boundary conditions data, which are based on measurement or whole building hygrothermal modelling, to satisfactorily asses the moisture performance of a building enclosure and potential occupants health problems related to mould growth., Peer reviewed article, Published.
New approaches to designing genes by evolution in the computer
The field of Evolutionary Computation (EC) has been inspired by ideas from the classical theory of biological evolution, with, in particular, the components of a population from which reproductive parents are chosen, a reproductive protocol, a method for altering the genetic information of offspring, and a means for testing the fitness of offspring in order to include them in the population. In turn, impressive progress in EC - understanding the reasons for efficiencies in evolutionary searches - has begun to influence scientific work in the field of molecular evolution and in the modeling of biological evolution (Stemmer, 1994a,b; van Nimwegen et al. 1997; 1999; Crutchfield & van Nimwegen, 2001). In this chapter, we will discuss how developments in EC, particularly in the area of crossover operators for Genetic Algorithms (GA), provide new understanding of evolutionary search efficiencies, and the impacts this can have for biological molecular evolution, including directed evolution in the test tube. GA approaches have five particular elements: encoding (the ‘chromosome’); a population; a method for selecting parents and making a child chromosome from the parents' chromosomes; a method for altering the child’s chromosomes (mutation and crossover/recombination); criteria for fitness; and rules, based on fitness, by which offspring are included into the population (and parents retained). We will discuss our work and others’ on each of these aspects, but our focus is on the substantial efficiencies that can be found in the alteration of the child chromosome step. For this, we take inspiration from real biological reproduction mechanisms., Book chapter, Published.
Noise in the segmentation gene network of Drosophila, with implications for mechanisms of body axis specification
Specification of the anteroposterior (head-to-tail) axis in the fruit fly Drosophila melanogaster is one of the best understood examples of embryonic pattern formation, at the genetic level. A network of some 14 segmentation genes controls protein expression in narrow domains which are the first manifestation of the segments of the insect body. Work in the New York lab has led to a databank of more than 3300 confocal microscope images, quantifying protein expression for the segmentation genes, over a series of times during which protein pattern is developing (http://flyex.ams.sunysb.edu/FlyEx/). Quantification of the variability in expression evident in this data (both between embryos and within single embryos) allows us to determine error propagation in segmentation signalling. The maternal signal to the egg is highly variable, with noise levels more than several times those seen for expression of downstream genes. This implies that error suppression is active in the embryonic patterning mechanism. Error suppression is not possible with the favoured mechanism of local concentration gradient reading for positional specification. We discuss possible patterning mechanisms which do reliably filter input noise., Peer-reviewed article, Published.
NRC-IRC develops evaluation protocol for innovative vapour barrier
Vapour barriers were originally intended to keep building assemblies from getting wet, but they can sometimes end up preventing assemblies from drying out. An innovative new product to manage moisture accumulation in the building envelope, however, may be able to address both issues: while the product acts as a vapour barrier under most conditions, it also allows excess moisture to escape. The Canadian Construction Materials Centre (CCMC) set out to determine whether this product can serve as a vapour barrier and an air barrier system and whether it conformed to the intent of applicable building code requirements. In collaboration with NRC-IRC researchers, CCMC developed a testing protocol for its evaluation, which was based on laboratory testing requirements for vapour diffusion, air leakage control and durability., Article, Published.
On keeping secrets
Proceedings of the 2015 Workshops at the Twenty-Ninth AAAI Conference on Artificial Intelligence in Austin, USA, 2015. Communication involves transferring information from one agent to another. An intelligent agent, either human or machine, is often able to choose to hide information in order to protect their interests. The notion of information hiding is closely linked to secrecy and dishonesty, but it also plays an important role in domains such as software engineering. In this paper, we consider the ethics of information hiding, particularly with respect to intelligent agents. In other words, we are concerned with situations that involve a human and an intelligent agent with access to different information. Is the intelligent agent justified in preventing a human user from accessing the information that they possess? This is trivially true in the case where access control systems exist. However, we are concerned with the situation where an intelligent agent is able to using a reasoning system to decide not to share information with all humans. On the other hand, we are also concerned with situations where humans hide information from machines. Are we ever under a moral obligation to share information with a computional agent? We argue that questions of this form are increasingly important now, as people are increasingly willing to divulge private information to machines with a great capacity to reason with that information and share it with others., Conference paper, Published.
On the representation and verification of cryptographic protocols in a theory of action
Proceedings of 2010 Eighth Annual International Conference on Privacy Security and Trust (PST) in Ottawa, ON, Canada, 17-19 Aug. 2010. Cryptographic protocols are usually specified in an informal, ad hoc language, with crucial elements, such as the protocol goal, left implicit. We suggest that this is one reason that such protocols are difficult to analyse, and are subject to subtle and nonintuitive attacks. We present an approach for formalising and analysing cryptographic protocols in a theory of action, specifically the situation calculus. Our thesis is that all aspects of a protocol must be explicitly specified. We provide a declarative specification of underlying assumptions and capabilities in the situation calculus. A protocol is translated into a sequence of actions to be executed by the principals, and a successful attack is an executable plan by an intruder that compromises the specified goal. Our prototype verification software takes a protocol specification, translates it into a high-level situation calculus (Golog) program, and outputs any attacks that can be found. We describe the structure and operation of our prototype software, and discuss performance issues., Conference paper, Published.
Optimal scaling of weight and waist circumference to height for adiposity and cardiovascular disease risk in individuals with spinal cord injury
Study Design: Observational cross-sectional study. Objectives: Body mass index (BMI), measured as a ratio of weight (Wt) to the square of height (Wt/Ht(2)), waist circumference (WC) and waist-to-height ratio (WHtR) are common surrogate measures of adiposity. It is not known whether alternate scaling powers for height might improve the relationships between these measures and indices of obesity or cardiovascular disease (CVD) risk in individuals with spinal cord injury (SCI). We aimed to estimate the values of 'x' that render Wt/Ht(x) and WC/Ht(x) maximally correlated with dual energy x-ray absorptiometry (DEXA) total and abdominal body fat and Framingham Cardiovascular Risk Scores. Setting: Canadian public research institution. Methods: We studied 27 subjects with traumatic SCI. Height, Wt and body fat measurements were determined from DEXA whole-body scans. WC measurements were also obtained, and individual Framingham Risk Scores were calculated. For values of 'x' ranging from 0.0 to 4.0, in increments of 0.1, correlations between Wt/Ht(x) and WC/Ht(x) with total and abdominal body fat (kg and percentages) and Framingham Risk Scores were computed. Results: We found that BMI was a poor predictor of CVD risk, regardless of the scaling factor. Moreover, BMI was strongly correlated with measures of obesity, and modification of the scaling factor from the standard (Wt/Ht(2)) is not recommended. WC was strongly correlated with both CVD risk and obesity, and standard measures (WC and WHtR) are of equal predictive power. Conclusion: On the basis of our findings from this sample, alterations in scaling powers may not be necessary in individuals with SCI; however, these findings should be validated in a larger cohort., Peer-reviewed article, Published. Received 25 February 2014; revised 1 May 2014; accepted 1 August 2014; published online 30 September 2014.

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