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Evaluation of tank car sloshing effects on rail safety
No full textNational Research Council Canada (NRC) was commissioned by Transport Canada (TC) to gather any evidence that movement of liquid in a rail tank car could contribute or is contributing in any way to derailments of trains carrying liquid dangerous goods. A literature review was performed to determine the state-of-the-art in sloshing research and identify gaps in existing research related to tank car sloshing. Over 70 references were examined. A variety of applications were covered by the review including rail transport, road vehicles, aerospace and marine transport. Representatives from companies that load or ship liquid dangerous goods were consulted to determine if liquid dangerous goods are shipped in partially filled cars, and, if they are, what the typical frequency of partial-fill shipments is and what the typical fill level is. Canadian accident and incident data from the Transportation Safety Board of Canada (TSB) were reviewed to determine if sloshing has ever been mentioned or suspected as a contributing factor in an incident. Individuals from TC, TSB, United States Federal Railroad Administration, Association of American Railroads, and the rail industry were consulted to determine if unreported evidence of sloshing had occurred in the past. Analytical work was conducted to study the effect of tank car sloshing on derailment risk. A multibody dynamics (MBD) liquid sloshing model was developed for a railway tank car with formulas generated based on available Finite Element Analysis data. The new liquid sloshing model was integrated into an empty tank car MBD simulation model developed in 2009-12 to study the impact of curvature on track geometry safety standards. The ability of the empty tank car model to predict wheel forces accurately in curves was validated previously on more than 523 miles of track with 1,340 curves. The integration of the liquid sloshing model and empty tank car model provided an MBD model capable of accurately predicting the dynamic behaviour of a tank car with a wide range of liquid payloads as it travelled over the field-test track. For comparison purposes, a solid-payload tank car model was developed by taking the validated empty tank car model and adding a non-moving payload located in the bottom of the tank. Hundreds of thousands of dynamic simulations were conducted for the tank car with liquid cargo at various fill ratios and with the equivalent solid cargo on more than 1,000 measured curves. The results show that under some conditions tank car sloshing could increase the risk of derailment. The detrimental effect of tank car sloshing on rail safety increases with the increase of outage, trailing tonnage, grade, car length difference, track curvature and train speed. It is recommended that further investigation be performed to improve the liquid-slosh model and develop a tool that can be used by regulators and railroads to develop improved guidelines on train marshalling practices.On the title page: Prepared for: Mr. Christopher Kirney, Transport Dangerous Goods Directorate, Transport CanadaSur la page de titre: Prepared for: Mr. Christopher Kirney, Transport Dangerous Goods Directorate, Transport CanadaPeer reviewed: NoNRC publication: Ye
Collision induced dissociation mass spectrometry challenge
No full textPeer reviewed: YesNRC publication: Ye
Examining gender and race bias in two hundred sentiment analysis systems
No full textAutomatic machine learning systems can inadvertently accentuate and perpetuate inappropriate human biases. Past work on examining inappropriate biases has largely focused on just individual systems. Further, there is no benchmark dataset for examining inappropriate biases in systems. Here for the first time, we present the Equity Evaluation Corpus (EEC), which consists of 8,640 English sentences carefully chosen to tease out biases towards certain races and genders. We use the dataset to examine 219 automatic sentiment analysis systems that took part in a recent shared task, SemEval-2018 Task 1 'Affect in Tweets'. We find that several of the systems show statistically significant bias; that is, they consistently provide slightly higher sentiment intensity predictions for one race or one gender. We make the EEC freely available.Peer reviewed: NoNRC publication: Ye
Complementary methods for the determination of the just-suspended speed and suspension state in a viscous solid\u2013liquid mixing system
No full textA poor understanding of mixing dynamics may lead to major economic losses in numerous industries due to poor yields and waste of raw materials. Then processes can be optimized through a better understanding of solid\u2013liquid mixing dynamics. Previous studies have characterized the suspension of solid particles in a viscous medium using a standard high shear impeller (a pitched-blade turbine or PBT) and have measured the fraction of suspended particles using the pressure gauge technique (PGT). Since the PGT cannot be applied in a straightforward way to close-clearance impellers, we developed a novel technique based on the PGT to determine the fraction of suspended particles in a system using a close-clearance impeller such as a double helical ribbon (DHR). We studied a solid\u2013liquid suspension in the laminar and transitional regimes with high particle loadings and a DHR. Since the dynamic pressure cannot be subtracted from the total pressure determined by the PGT, we developed two alternative methods. The first was the pressure difference method, which we used to determine a range of speeds where Njs is located. The second was the sedimentation-based method which we used to accurately quantify Njs and effectively eliminate the dynamic pressure. Their pertinence and applicability were demonstrated.Peer reviewed: YesNRC publication: Ye
Computational aeroelastic analysis using an enhanced OpenFOAM-based CFD-CSD solver
No full textIn this paper, the development of a coupled solver suitable for the simulation of unsteady transonic aerodynamicow is described. The OpenFOAM baseline segregated solver, rho-CentralFoam, is modied to produce an implicit Euler formulation where the conservation of mass, momentum and energy equations are solved in a coupled manner. The key modication centers on the construction of the convectiveux Jacobian matrix and the application of the Lower-Upper Symmetric Gauss-Seidel algorithm to solve the resultant matrix. The developed aerodynamic solver is then coupled with a modied OpenFOAM structural solver sixDoFRigidBodyMotion to formulate a full aeroelastic model. This model is veried through the simulation of two benchmark problems: a pitching and uttering 2D NACA64A010 airfoil, and the Benchmark Supercritical Wing (BSCW) from the second AIAA Aeroelastic Prediction Workshop (AePW-2). In all cases, the numerical solutions of the Euler equations show good agreement with the available numerical and experimental data.Peer reviewed: YesNRC publication: Ye
Cognitive biases within decision making during fire evacuations
No full textDuring a fire evacuation, once an individual perceives cues from a fire event, they must interpret them to assess the new situation and determine whether action is required. It is proposed that this assessment and action selection can employ either an automatic or reflective processing system depending on the nature of the situation and the experiences of the individual involved. This decision-making process is bounded in terms of the information available, the time available, and an individual\u2019s resources to process such information that influences which processing mechanism is adopted. To compensate for such limitations and manage the uncertainty and complexity associated with the decision-making process, people may employ heuristics that reduce decision-making from a cognitively effortful problem-solving task requiring mental reflection, to a less effortful pattern-matching process, where stored conditions and expectations are quickly scanned to identify relevant responses. During this decision-making process cognitive biases may occur which cause an individual to neglect or be biased towards certain information: this may potentially lead to an inappropriate and/or unexpected response. Cognitive biases affect performance without the individual being directly aware of them. This paper identifies cognitive biases from existing literature that may influence a person\u2019s decision-making process during a fire evacuation, along with how these align with general decision-making in the process. The purpose of the article is to promote consideration of cognitive biases in the modeling of evacuee behavior, as well as during the fire safety design of buildings and evacuation procedures.Correction to: Cognitive Biases Within Decision Making During Fire Evacuations, at https://doi.org/10.1007/s10694-018-0722-2Peer reviewed: YesNRC publication: Ye
GPI Spectra of HR 8799 c, d, and e from 1.5 to 2.4 \u3bcm with KLIP Forward Modeling
No full textWe explore KLIP forward modeling spectral extraction on Gemini Planet Imager coronagraphic data of HR 8799, using PyKLIP, and show algorithm stability with varying KLIP parameters. We report new and re-reduced spectrophotometry of HR 8799 c, d, and e in the H and K bands. We discuss a strategy for choosing optimal KLIP PSF subtraction parameters by injecting simulated sources and recovering them over a range of parameters. The K1/K2 spectra for HR 8799 c and d are similar to previously published results from the same data set. We also present a K-band spectrum of HR 8799 e for the first time and show that our H-band spectra agree well with previously published spectra from the VLT/SPHERE instrument. We show that HR 8799 c and d show significant differences in their H and K spectra, but do not find any conclusive differences between d and e, nor between c and e, likely due to large error bars in the recovered spectrum of e. Compared to M-, L-, and T-type field brown dwarfs, all three planets are most consistent with mid- and late-L spectral types. All objects are consistent with low gravity, but a lack of standard spectra for low gravity limit the ability to fit the best spectral type. We discuss how dedicated modeling efforts can better fit HR 8799 planets' near-IR flux, as well as how differences between the properties of these planets can be further explored.Peer reviewed: YesNRC publication: Ye
Influence of primary particle polydispersity and overlapping on soot morphological parameters derived from numerical TEM images
No full textExperimental studies of soot morphology based on analysis of transmission electron microscopy (TEM) images usually neglect the potential effects of primary particle polydispersity and overlapping. In this study, fractal aggregates of different sizes consisting of polydisperse and overlapping primary particles were numerically generated using typical fractal dimension and prefactor relevant to soot. A total of 3600 simulated two-dimensional projections for each primary particle size distribution and level of overlapping considered was produced and analyzed using two TEM image analysis methods commonly used in the literature to evaluate the effects of primary particle polydispersity and overlapping on the recovered morphological parameters of soot. Fairly large deviations in the recovered number of primary particles in aggregates were obtained by both methods considered using the procedure commonly used in the literature. A recommendation was proposed to improve the accuracy of the retrieved number of polydisperse primary particles in an aggregate. We show that the results obtained by using both the Tian et al. (2006) and Brasil et al. (1999) methods can be significantly improved by using the recommended modification for primary particle polydispersity levels commonly encountered in flame soot. Finally, we recommend to use the modified Tian et al. 2006 method for recovering the number of primary particles of aggregates consisting of both polydisperse and overlapped primary particles.Peer reviewed: YesNRC publication: Ye