493 research outputs found
Local Buckling Design Rules for Profiled Sandwich Panels based on the Studies of Foam–filled Steel Beams
No full textModern composite sandwich constructions have been used very successfully in many aerospace and structural applications. Various aspects of structural behaviour of sandwich panels have been researched for many decades as they are a potential load carrying component in buildings. Sandwich panels exhibit various types of buckling failure modes depending on the types of steel faces used. Local buckling is one of the fundamental failure modes of sandwich panels with profiled faces. To investigate the local buckling behaviour, Davies and Hakmi (1992) conducted a series of bending tests of foam-filled thin-walled steel beams and developed a design method, which is now adopted in the European recommendations for the design of sandwich panels (CIB, 2000). However, recent studies by Pokharel and Mahendran (2003, 2004a, 2004b) have shown that this design method is inadequate for sandwich panels with very slender plate elements, and therefore developed a new design rule that is applicable for a wide range of width to thickness (b/t) ratios of foam supported plate elements. This research was undertaken to investigate the applicability of these design rules based on the results from Davies and Hakmi’s (1992) bending tests of foam-filled steel beams and a numerical study simulating the bending tests. Both the experimental and numerical results were then compared with the predictions from the current and newly developed design rules. This paper presents the details of Davies and Hakmi’s (1992) bending tests and corresponding numerical modelling, evaluation and comparison of results
Electrochemomechanics in Mixed Ionic Electronic Conductors and solid oxide cells
No full textThis thesis presents a model for coupled electrochemomechanics in Mixed Ionic Electronic Conductors (MIEC). A continuum model is formulated to simulate the transport of ionic defects and the stress distribution in the conductor arising from the chemical expansion associated with the defects. First, a finite element formulation of the model is developed and validated with various analytical solutions and comparisons with experimental results. In the third chapter the coupled model is used along with an iterative scheme to simulate the transport characteristics in solid oxide cells with oxygen surface exchange and results are compared with experimental cell operation. The model is used to study the effect of oxygen surface exchange and the bulk diffusion of defects on the performance of solid oxide cell. In the fourth chapter, the transport of ionic defects is studied under spatially varying oxygen surface exchange in solid oxide cells due to the presence of metal current collector. Various defect transport mechanisms (boundary value problem setups) are proposed and studied to identify and explain the influence of metal current collector on oxygen exchange at the electrode film surface.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2022-08-01The student, Rupesh Kumar Mahendran, accepted the attached license on 2020-07-21 at 16:46.The student, Rupesh Kumar Mahendran, submitted this Thesis for approval on 2020-07-21 at 17:01.This Thesis was approved for publication on 2020-07-24 at 10:34.DSpace SAF Submission Ingestion Package generated from Vireo submission #15716 on 2020-10-02 at 15:34:04Made available in DSpace on 2020-10-07T22:44:46Z (GMT). No. of bitstreams: 3
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Previous issue date: 2020-07-24Embargo set by: Seth Robbins for item 116264
Lift date: 2022-10-07T22:44:53Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Onl
Assessment and application of non-technical skills in robotic-assisted surgery: a systematic review.
No full textOpen Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.Background: Undeniably, robotic-assisted surgery (RAS) has become very popular in recent decades, but it has introduced challenges to the workflow of the surgical team. Non-technical skills (NTS) have received less emphasis than technical skills in training and assessment. The systematic review aimed to update the evidence on the role of NTS in robotic surgery, specifically focusing on evaluating assessment tools and their utilisation in training and surgical education in robotic surgery.
Methods: A systematic literature search of PubMed, PsycINFO, MEDLINE, and EMBASE was conducted to identify primary articles on NTS in RAS. Messick's validity framework and the Modified Medical Education Research Study Quality Instrument were utilised to evaluate the quality of the validity evidence of the abstracted articles.
Results: Seventeen studies were eligible for the final analysis. Communication, environmental factors, anticipation and teamwork were key NTS for RAS. Team-related factors such as ambient noise and chatter, inconveniences due to repeated requests during the procedure and constraints due to poor design of the operating room may harm patient safety during RAS. Three novel rater-based scoring systems and one sensor-based method for assessing NTS in RAS were identified. Anticipation by the team to predict and execute the next move before an explicit verbal command improved the surgeon's situational awareness.
Conclusion: This systematic review highlighted the paucity of reporting on non-technical skills in robotic surgery with only three bespoke objective assessment tools being identified. Communication, environmental factors, anticipation, and teamwork are the key non-technical skills reported in robotic surgery, and further research is required to investigate their benefits to improve patient safety during robotic surgery
Antibiotic Permeation across the OmpF Channel: Modulation of the Affinity Site in the Presence of Magnesium
No full textWe characterize the rate-limiting interaction of the antibiotic
10 enrofloxacin with OmpF, a channel from the outer cell wall of Escherichia coli.
11 Reconstitution of a single OmpF trimer into planar lipid membranes allows
12 measurement of the ion current through the channel. Penetration of antibiotics causes
13 ion current blockages, and their frequency allows a conclusion on the kinetics of
14 channel entry and exit. In contrast to other antibiotics, enrofloxacin is able to block the
15 OmpF channel for several milliseconds, reflecting high affinities comparable to
16 substrate-specific channels such as the maltodextrin-specific maltoporin. Surprisingly,
17 the presence of a divalent ion such as Mg2+ leads to fast flickering with an increase in
18 the rates of association and dissociation. All-atom computer modeling provides the
19 most probable pathway able to identify the relevant rate-limiting interaction during antibiotic permeation. Mg2+ has a high affinity
20 for the aspartic acid at the 113 position (D113) in the center of the OmpF intracellular binding site. Therefore, the presence of Mg2+
21 reverses the charge and enrofloxacin may cross the constriction region in its favorable orientation with the carboxylic group first
Refined Plastic Hinge Analysis of Steel Frame Structures Subjected to Lateral Torsional Buckling Effects
No full textSection moment capacity tests of hollow flange steel plate girders
No full textHollow flange steel plate girders (HFSPG) are built-up hollow flange I-girders formed by welding currently available cold-formed rectangular hollow sections (RHS) to a web plate. It is intended to gain the advantages of both I-sections and hollow sections with additional desired performances due to its orientation. HFSPGs can meet the increased demand of an effective member for long span applications. Further, the introduced HFSPG will be an innovative, efficient and cost effective replacement for conventionally used universal beams (UB) and welded beams (WB). Although the HFSPG provides favorable properties, it is vulnerable to buckling failures which can limit its flexural capacity. Therefore, an investigation was conducted to study the section moment capacities of HFSPGs using both experiments and finite element analyses. The ultimate moment capacities from the tests and analyses were compared with the predictions from the current design\ud
rules. This paper presents the details of the experimental and finite element studies and the results
Fire performance of LSF walls made of hollow flange channel studs
No full text<b>Purpose</b>\ud
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This paper presents an investigation conducted to evaluate the effects of important parameters affecting the structural fire performance of LSF walls. It also evaluates the applicability of commonly used critical hot flange temperature method to determine the <i>Fire Resistance Ratings</i> (FRR) of different LSF walls. \ud
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<b>Design/methodology/approach</b>\ud
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The effects of important parameters such as stud section profiles and their dimensions, elevated temperature mechanical property reduction factors of the steel used, types of wall configurations and fire curves on the FRR of LSF walls were investigated. An extensive finite element analysis based parametric study was conducted to evaluate their effects. For this purpose, finite element models which were validated using the full scale fire test results were used. Using the structural capacities obtained from finite element analyses, the load ratio versus FRR curves were produced for all the different LSF walls considered. \ud
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<b>Findings</b>\ud
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Stud depth and thickness significantly affected the fire performance of LSF walls due to the differences in temperature development pattern, thermal bowing deflections and the failure modes of stud. The FRR of LSF walls increased significantly when steel studs with higher elevated temperature mechanical property reduction factors were used. FRR significantly changed when realistic design fire curves were used instead of the standard fire curve. Furthermore, both the critical hot and average flange temperature methods were found to be unsuitable to predict the FRR of LSF walls. \ud
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<b>Originality/value</b>\ud
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The developed comprehensive fire performance data would facilitate the development of LSF walls with enhanced fire performance and importantly it would facilitate and advance the successful applications of HFC section studs in LSF walls. © Emerald Group Publishing Limited
Local plastic mechanisms in thin steel plates under in-plane compression
No full textThin-walled steel plates subjected to in-plane compression develop two types of local plastic mechanism, namely the roof-shaped mechanism and the so-called flip-disc mechanism, but the intriguing question of why two mechanisms should develop was not answered until recently. It was considered that the location of first yield point shifted from the centre of the plate to the midpoint of the longitudinal edge depending on the b/t ratio, imperfection level, and yield stress of steel, which then decided the type of mechanism. This paper has verified this hypothesis using analysis and laboratory experiments. An elastic analysis using Galerkin's method to solve Marguerre's equations was first used to determine the first yield point, based on which the local plastic mechanism/imperfection tolerance tables have been developed which give the type of mechanism as a function of b/t ratio, imperfection level and yield stress of steel. Laboratory experiments of thin-walled columns verified the imperfection tolerance tables and thus indirectly the hypothesis. Elastic and rigid-plastic curves were them used to predict the effect on the ultimate load due to the change of mechanism. A finite element analysis of selected cases also confirmed the results from simple analyses and experiments
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