BCIT Citations Collection
Collection of published works from BCIT researchers, faculty, and instructors.
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- Assessment of thermal comfort during surgical operations
- The thermal environment was studied in two operating rooms at the Montreal General Hospital. Thermal comfort of the staff was assessed based on measurements of the environment during surgical operations and on questionnaires given to the staff. Infrared pictures of representative surfaces and people were also taken and, when possible, skin and core temperatures of the patient were also measured. The thermal resistance of clothing and the activity levels for all the people were estimated from published tables and previous research studies. Three thermal zones were studied: zone 1, bounded by the patient, the surgical staff, and the surgical lights; zone 2, the adjacent area; and zone 3, the farthest one. It was found that under the present environmental and personal conditions it is not possible to provide all groups of people with an acceptable thermal environment. In general, surgeons tend to feel from slightly warm to hot (they sweat very often), anesthesia staff and nurses from slightly cool to cold, and the patient from slightly cool to very cold (patients sometimes woke up shivering). In addition to questionnaires, thermal comfort was predicted based on Fanger ' PMV model, which assumes a uniform thermal environment. Based on Fanger's model, the air temperature that could have ensured satisfactory thermal comfort for the surgeon, under the particular conditions studied, was about 66 deg F (19 deg C). However, at that temperature, to remain in good thermal comfort, nurses and anesthetists must be clothed with at least 0.9 clo and the patient covered with at least 1.6 clo. In practice, however, the radiant temperature asymmetry from the surgical lights in zone 1, which ranges between 11 deg F (6 deg C) and 137 (7 deg C) over the operating table and between 18 deg F (1O deg C) and 22F (12 deg C) over the floor (at a level of 1.1 m), causes surgeons' dissatisfaction with the environment at any air temperature. Possible solutions to minimize radiation and its effects on the surgeons are discussed, which would permit ambient temperatures more favorable for the patient and all the staff., Peer reviewed, Conference proceeding, Published: 2001.
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- Attic baffle size and vent configuration impacts on attic ventilation
- The international residential code (IRC) and most building codes in North America provide attic ventilation codes which allow a certain minimum venting area with an unblocked space by the ceiling insulation. Most of these codes have similar minimum venting ratio, minimum space gap between the roof sheathing and ceiling insulation and vent area location for similar climatic conditions. In this paper, the effects of varying the gap between roof sheathing and ceiling insulation (baffle size) and the locations of vent area under both summer and winter conditions are investigated. Three different baffle sizes and three different locations of the attic vent are used to study their effect on the air distribution and temperature profile inside the attic space. A CFD model is developed and validated using existing experimental measurements. Results show that increasing baffle size hugely affects the air distribution when the air flow is majorly driven by wind. The upper side roof vents have been located at three different locations and our findings show when the upper vent is placed the furthest from the ridge the Air Change per Hour (ACH) value in the attic increases but the air circulation is minimal in the top parts of the attic space and structural elements., Peer-reviewed article, Published. Received 29 November 2014, Revised 26 January 2015, Accepted 28 January 2015, Available online 7 February 2015.
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- Belief change and cryptographic protocol verification
- Proceedings of the 22nd Conference on Artificial Intelligence (AAAI-07) in Vancouver, BC, July 22–26, 2007. Cryptographic protocols are structured sequences of messages that are used for exchanging information in a hostile environment. Many protocols have epistemic goals: a successful run of the protocol is intended to cause a participant to hold certain beliefs. As such, epistemic logics have been employed for the verification of cryptographic protocols. Although this approach to verification is explicitly concerned with changing beliefs, formal belief change operators have not been incorporated in previous work. In this paper, we introduce a new approach to protocol verification by combining a monotonic logic with a non-monotonic belief change operator. In this context, a protocol participant is able to retract beliefs in response to new information and a protocol participant is able to postulate the most plausible event explaining new information. We illustrate that this kind of reasoning is particularly important when protocol participants have incorrect beliefs., Conference paper, Published.
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- Belief change in the context of fallible actions and observations
- Proceedings of the 21st Conference on Artificial Intelligence (AAAI-06). Boston, MA, July 16–20, 2006. We consider the iterated belief change that occurs following an alternating sequence of actions and observations. At each instant, an agent has some beliefs about the action that occurs as well as beliefs about the resulting state of the world. We represent such problems by a sequence of ranking functions, so an agent assigns a quantitative plausibility value to every action and every state at each point in time. The resulting formalism is able to represent fallible knowledge, erroneous perception, exogenous actions, and failed actions. We illustrate that our framework is a generalization of several existing approaches to belief change, and it appropriately captures the non-elementary interaction between belief update and belief revision., Conference paper, Published.
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- Belief change with uncertain action histories
- We consider the iterated belief change that occurs following an alternating sequence of actions and observations. At each instant, an agent has beliefs about the actions that have occurred as well as beliefs about the resulting state of the world. We represent such problems by a sequence of ranking functions, so an agent assigns a quantitative plausibility value to every action and every state at each point in time. The resulting formalism is able to represent fallible belief, erroneous perception, exogenous actions, and failed actions. We illustrate that our framework is a generalization of several existing approaches to belief change, and it appropriately captures the non-elementary interaction between belief update and belief revision., Peer-reviewed article, Published.
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- Belief manipulation and message meaning for protocol analysis
- Agents often try to convince others to hold certain beliefs. In fact, many network security attacks can actually be framed in terms of a dishonest that is trying to get an honest agent to believe some particular, untrue claims. While the study of belief change is an established area of research in Artificial Intelligence, there has been comparatively little exploration of the way one agent can explicitly manipulate the beliefs of another. In this paper, we introduce a precise, formal notion of a belief manipulation problem. We also illustrate that the meaning of a message can be parsed into different communicative acts, as defined in discourse analysis theory. Specifically, we suggest that each message can be understood in terms of what it says about the world, what it says about the message history, and what it says about future actions. We demonstrate that this kind of dissection can actually be used to discover the goals of an intruder in a communication session, which is important when determining how an adversary is trying to manipulate the beliefs of an honest agent. This information will then help prevent future attacks. We frame the discussion of belief manipulation primarily in the context of cryptographic protocol analysis., Peer-reviewed article, Published. Received: 17 January 2014; Accepted: 29 September 2014; Published: 10 October 2014.
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- Belief manipulation through propositional announcements
- Proceedings of the Twenty-Sixth International Joint Conference on Artificial Intelligence (IJCAI-17) in Melbourne, Australia 19-25 August 2017. Public announcements cause each agent in a group to modify their beliefs to incorporate some new piece of information, while simultaneously being aware that all other agents are doing the same. Given a set of agents and a set of epistemic goals, it is natural to ask if there is a single announcement that will make each agent believe the corresponding goal. This problem is known to be undecidable in a general modal setting, where the presence of nested beliefs can lead to complex dynamics. In this paper, we consider not necessarily truthful public announcements in the setting of AGM belief revision. We prove that announcement finding in this setting is not only decidable, but that it is simpler than the corresponding problem in the most simplified modal logics. We then describe an implemented tool that uses announcement finding to control robot behaviour through belief manipulation., Conference paper, Published.
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- Belief modeling for maritime surveillance
- Proceedings of 12th International Conference on Information Fusion, 2009, FUSION '09 in Seattle, WA, USA, 6-9 July 2009. In maritime surveillance, the volume of information to be processed is very large and there is a great deal of uncertainty about the data. There are many vessels at sea at every point in time, and the vast majority of them pose no threat to security. Sifting through all of the benign activity to find unusual activities is a difficult problem. The problem is made even more difficult by the fact that the available data about vessel activities is both incomplete and inconsistent. In order to manage this uncertainty, automated anomaly detection software can be very useful in the early detection of threats to security. This paper introduces a high-level architecture for an anomaly detection system based on a formal model of beliefs with respect to each entity in some domain of interest. In this framework, the system has beliefs about the intentions of each vessel in the maritime domain. If the vessel behaves in an unexpected manner, these intentions are revised and a human operations centre worker is notified. This approach is flexible, scalable, and easily manages inconsistent information. Moreover, the approach has the pragmatic advantage that it uses expert information to inform decision making, but the required information is easily obtained through simple ranking exercises., Conference paper, Published.
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- Belief revision and trust
- Proceedings of the 15th International Workshop on Non-Monotonic Reasoning (NMR 2014), Vienna, Austria, 17–19 July 2014. Belief revision is the process in which an agent incorporates a new piece of information together with a pre-existing set of beliefs. When the new information comes in the form of a report from another agent, then it is clear that we must first determine whether or not that agent should be trusted. In this paper, we provide a formal approach to modeling trust as a pre-processing step before belief revision. We emphasize that trust is not simply a relation between agents; the trust that one agent has in another is often restricted to a particular domain of expertise. We demonstrate that this form of trust can be captured by associating a state-partition with each agent, then relativizing all reports to this state partition before performing belief revision. In this manner, we incorporate only the part of a report that falls under the perceived domain of expertise of the reporting agent. Unfortunately, state partitions based on expertise do not allow us to compare the relative strength of trust held with respect to different agents. To address this problem, we introduce pseudometrics over states to represent differing degrees of trust. This allows us to incorporate simultaneous reports from multiple agents in a way that ensures the most trusted reports will be believed., Conference paper, Published.
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- Belief revision on modal accessibility relations
- Proceedings of the 6th International Conference on Agents and Artificial Intelligence in Angers, France, 2014. In order to model the changing beliefs of an agent, one must actually address two distinct issues. First, one must devise a model of static beliefs that accurately captures the appropriate notions of incompleteness and uncertainty. Second, one must define appropriate operations to model the way beliefs are modified in response to different events. Historically, the former is addressed through the use of modal logics and the latter is addressed through belief change operators. However, these two formal approaches are not particularly complementary; the normal representation of belief in a modal logic is not suitable for revision using standard belief change operators. In this paper, we introduce a new modal logic that uses the accessibility relation to encode epistemic entrenchment, and we demonstrate that this logic captures AGM revision. We consider the suitability of our new representation of belief, and we discuss potential advantages to be exploited in future work., Conference paper, Published.
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- Biomechanical characteristics, patient preference and activity level with different prosthetic feet
- Providing appropriate prosthetic feet to those with limb loss is a complex and subjective process influenced by professional judgment and payer guidelines. This study used a small load cell (Europa™) at the base of the socket to measure the sagittal moments during walking with three objective categories of prosthetic feet in eleven individuals with transtibial limb loss with MFCL K2, K3 and K4 functional levels. Forefoot stiffness and hysteresis characteristics defined the three foot categories: Stiff, Intermediate, and Compliant. Prosthetic feet were randomly assigned and blinded from participants and investigators. After laboratory testing, participants completed one week community wear tests followed by a modified prosthetics evaluation questionnaire to determine if a specific category of prosthetic feet was preferred. The Compliant category of prosthetic feet was preferred by the participants (P=0.025) over the Stiff and Intermediate prosthetic feet, and the Compliant and Intermediate feet had 15% lower maximum sagittal moments during walking in the laboratory (P=0.0011) compared to the Stiff feet. The activity level of the participants did not change significantly with any of the wear tests in the community, suggesting that each foot was evaluated over a similar number of steps, but did not inherently increase activity. This is the first randomized double blind study in which prosthetic users have expressed a preference for a specific biomechanical characteristic of prosthetic feet: those with lower peak sagittal moments were preferred, and specifically preferred on slopes, stairs, uneven terrain, and during turns and maneuvering during real world use., Peer-reviewed article, Published.
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- Bluetooth for decoy systems
- Proceedings of 2017 IEEE Conference on Communications and Network Security (CNS) in Las Vegas, NV, USA, USA, 9-11 Oct. 2017. We present an approach to tracking the behaviour of an attacker on a decoy system, where the decoy communicates with the real system only through low energy bluetooth. The result is a low-cost solution that does not interrupt the live system, while limiting potential damage. The attacker has no way to detect that they are being monitored, while their actions are being logged for further investigation. The system has been physically implemented using Raspberry PI and Arduino boards to replicate practical performance., Conference paper, Published.