Toward Machine Learned Highly Reduce Kinetic Models For Methane/Air Combustion

Accurate low dimension chemical kinetic models for methane are an essential component in the design of efficient gas turbine combustors. Kinetic models coupled to computational fluid dynamics (CFD) provide quick and efficient ways to test the effect of operating conditions, fuel composition and combustor design compared to physical experiments. However, detailed chemical kinetic models are too computationally expensive for use in CFD. We propose a novel data orientated three-step methodology to produce compact models that replicate a target set of detailed model properties to a high fidelity. In the first step, a reduced kinetic model is obtained by removing all non-essential species from the detailed model containing 118 species using path flux analysis (PFA). It is then numerically optimised to replicate the detailed model's prediction in two rounds; First, to selected species (OH,H,CO and CH4) profiles in perfectly stirred reactor (PSR) simulations and then re-optimised to the detailed model's prediction of the laminar flame speed. This is implemented by a purposely developed Machine Learned Optimisation of Chemical Kinetics (MLOCK) algorithm. The MLOCK algorithm systematically perturbs all three Arrhenius parameters for selected reactions and assesses the suitability of the new parameters through an objective error function which quantifies the error in the compact model's calculation of the optimisation target. This strategy is demonstrated through the production of a 19 species and a 15 species compact model for methane/air combustion. Both compact models are validated across a range of 0D and 1D calculations across both lean and rich conditions and shows good agreement to the parent detailed mechanism. The 15 species model is shown to outperform the current state-of-art models in both accuracy and range of conditions the model is valid over.Comment: Conference Paper: ASME Turbo Expo 202

Gender disparities in OHNS residency awards

Gender disparities are well established in the surgical field, despite increasing prevalence of women in surgical specialties. This study aims to evaluate gender disparities in otolaryngology residency training with a focus on awards in residency. 122 OHNS training programs were sent emails with a survey link requesting participation. Questions including number of women residents as well as questions pertaining to specific awards were detailed. Primary outcome measures were total number and percentages of award recipients that were women. Further analysis stratification was completed for geographic location and award type. 15% of programs contacted participated in our survey. Data was gathered from 2010-2019. The percentage of women in a given OHNS residency program ranged from 0% to 55%. Awards distributed to women in a program ranged from 6% to 50%. Women were disproportionately awarded in all residency program except one, in which they were over-awarded. Overall, women were found to be 42% less likely to receive a residency award compared to men (OR, 0.58; 95% CI, 0.42 to 0.81; P = 0.001). Statistical significance was identified in awards of academic excellence, where women residents were found to be 54% less likely to receive an award, as well as in teaching awards, where women were 51% less likely to receive an award. When addressing whether the responder believed gender bias existed in otolaryngology residency, 58% felt there may be some bias, while 24% responded yes, and 12% responded no. Gender inequalities exist at several stages within an individual’s academic career including at the resident trainee level. This study demonstrates that women are disproportionately distributed residency awards when compared to their male colleagues in OHNS. Knowledge of these disparities must be made to prevent a negative long-standing impact on women residents within OHNS programs

Overview of Standards for Technological and Engineering Literacy (Other)

In 2020, the International Technology and Engineering Educators Association (ITEEA) published Standards for Technological and Engineering Literacy: The Role of Technology and Engineering in STEM Education (STEL) [1]. These standards open with a clear rationale why all Pk-12 students should study technology and engineering: Technology and engineering are pervasive in all aspects of our lives. Every human activity is dependent upon the products, systems, and processes created to help grow food, provide shelter, communicate, work, and recreate. As the world grows more complex, it is increasingly important for everyone to understand more about technology and engineering [1, p. 1]. The goal of STEL is not to turn Pk-12 students into technologists or engineers—although many students may end up pursuing these career paths—rather STEL was created to broaden all student’s technological and engineering literacy so they can make informed decisions about the technologies they encounter in the world around them, and better contribute to their design, development, and use. This paper will provide a brief history of Pk-12 technology and engineering standards in the United States, an overview of STEL [1], and recommendations for STEL implementation

Efforts Towards a Validated Time-Domain Model of an Oscillating Water Column with Control Components

As part of the development process of a proposed offshore floating wind/wave platform, a scale-model testing programme has been carried out at a narrow tank facility on a single oscillating water column (OWC) device. Previous proof-ofconcept testing was performed on a scale model of the proposed platform comprising thirty-two OWCs with control components. That testing programme, implemented at the Hydraulic and Maritime Research Centre, demonstrated the feasibility of the concept. However, the large number of interacting components in this complex system results in difficulties when attempting to study and model numerically the hydrodynamic and thermodynamic processes at work within the OWCs during operation. In order to better study these processes, the subsequent phase of narrow tank testing was planned based on a single-chamber OWC model as described herein. This model was constructed with similar dimensions and cross-sectional profile to that of one OWC chamber in the larger model. Various control components can be added to and removed from the new model to investigate in a systematic fashion the effect of each component. Theory to numerically model the OWC in various configurations has been developed. A comparison between the tank test results and those obtained for a specific setup is presented

Modelling and results for an array of 32 oscillating water columns

As part of an investigation into the feasibility of an offshore combined wind/wave energy converting platform, comprising one or more wind turbines mounted on a floating structure in which a number of oscillating water columns (OWCs) are embedded, testing was carried out on a 1:50 scale model of the wave energy converting component of the platform. The model comprises two legs joined at one end at an angle of 90 degrees. A form of soft latching is implemented through the use of high and low-pressure plenums to which the OWC chambers communicate via air admittance valves. The model was tested in a number of configurations, subject to varying amounts of simulated power take-off damping and over a range of incident regular-wave periods. Platform motions, OWC chamber and plenum pressure and water column motions were recorded for each test. This paper discusses some considerations in the design, construction, instrumentation and testing of the model. Thermodynamic theory describing the flow of air throughout the system, based on the conservation of mass, is developed and related to the motion of the water columns. Representative results from the model testing in the time domain are presented. Finally, some conclusions are drawn from these results

Production of ethyl acetate from pyrolysis of lignin model compound guaiacylglycerol-β-guaiacyl using TGA-MS

Due to the complex chemical structure of lignin, the fundamental chemistry underlying its pyrolysis behaviour is poorly understood. A detailed knowledge of this chemistry would allow for the construction of detailed predictive chemical kinetic models, which could be used to maximise the efficiency of the pyrolysis process. Lignin is comprised of three monolignols, guaiacyl, p-hydroxyphenyl and syringyl. These are joined together by aryl ether linkages of which β-O-4 is the most common, representing approximately 50% of the linkages found in lignin.[1] In this study, pyrolysis (20oC/minute heating rate) was carried out on a lignin model compound, guaiacylglycerol-β-guaiacyl ether (GGE). GGE is composed of two guaiacyl subunits connected by a β-O-4 linkage, making it broadly representative of the lignin motif and as such an important lignin model compound. A detailed understanding of the thermal degradation of GGE under pyrolysis conditions will provide valuable information of the role of the β-O-4 linkage in lignin. Please click Additional Files below to see the full abstract

Ab Initio and Kinetic Modelling of β\beta-D-xylopyranose Under Fast Pyrolysis Conditions

Lignocellulosic biomass is an abundant renewable resource that can be upgraded to chemical and fuel products through a range of thermal conversion processes. Fast pyrolysis is a promising technology that uses high temperatures and fast heating rates to convert lignocellulose into bio-oils in high yields in the absence of oxygen. Hemicellulose is one of three major components of lignocellulosic biomass and is a highly branched heteropolymer structure made of pentose, hexose sugars, and sugar acids. In this study, $\beta$-D-xylopyranose is proposed as a model structural motif for the essential chemical structure of hemicellulose. The gas-phase pyrolytic reactivity of $\beta$-D-xylopyranose is thoroughly investigated using computational strategies rooted in quantum chemistry. In particular, its thermal degradation potential energy surfaces are computed employing Minnesota global hybrid functional M06-2X in conjunction with 6-311++G(d,p) Pople basis set. Electronic energies are further refined by performing DLPNO-CCSD(T)-F12 single point calculations on top of M06-2X geometries using cc-pVTZ-F12 basis set. Key thermodynamic quantities (free energies, barrier heights, enthalpies of formation, and heat capacities) are computed. Rate coefficients for the initial steps of thermal decomposition are computed by means of reaction rate theory. For the first time, a detailed elementary reaction kinetic model for $\beta$-D-xylopyranose is developed by utilizing the thermodynamic and kinetic information acquired from the aforementioned calculations. This model specifically targets the initial stages of $\beta$-D-xylopyranose pyrolysis, aiming to gain a deeper understanding of its reaction kinetics. This approach establishes a systematic strategy for exploring reactive pathways, evaluating competing parallel reactions, and selectively accepting or discarding pathways based on the analysis.Comment: 37 pages, 7 figures, 5 table

Nasopharyngeal Swabs vs. Nasal Aspirates for Respiratory Virus Detection: A Systematic Review

Nasal pathogen detection sensitivities can be as low as 70% despite advances in molecular diagnostics. This may be linked to the choice of sampling method. A diagnostic test accuracy review for sensitivity was undertaken to compare sensitivity of swabbing to the nasopharynx and extracting nasal aspirates, using the PRISMA protocol, Cochrane rapid review methodology, and QUADAS-2 risk of bias tools, with meta-analysis of included studies. Sensitivities were calculated by a consensus standard of positivity by either method as the ‘gold standard.’ Insufficient sampling methodology, cross sectional study designs, and studies pooling samples across anatomical sites were excluded. Of 13 subsequently eligible studies, 8 had ‘high’ risk of bias, and 5 had ‘high’ applicability concerns. There were no statistical differences in overall sensitivities between collection methods for eight different viruses, and this did not differ with use of PCR, immunofluorescence, or culture. In one study alone, Influenza H1N1(2009) favored nasopharyngeal swabs, with aspirates having 93.3% of the sensitivity of swabs (p > 0.001). Similarly equivocal sensitivities were noted in reports detecting bacteria. The chain of sampling, from anatomical site to laboratory results, features different potential foci along which sensitivity may be lost. A fair body of evidence exists that use of a different sampling method will not yield more respiratory pathogens

Isoniazid concentrations in hair and plasma area-under-the-curve exposure among children with tuberculosis.

We measured hair and plasma concentrations of isoniazid among sixteen children with tuberculosis who underwent personal or video-assisted directly observed therapy and thus had 100% adherence. This study therefore defined typical isoniazid exposure parameters after two months of treatment among fully-adherent patients in both hair and plasma (plasma area under the concentration-time curve, AUC, estimated using pharmacokinetic data collected 0, 2, 4, and 6 hours after drug administration). We found that INH levels in hair among highly-adherent individuals did not correlate well with plasma AUC or trough concentrations, suggesting that each measure may provide incremental and complementary information regarding drug exposure in the context of TB treatment