56 research outputs found
Aircraft Disruption Management: Increasing Performance with Machine Learning Predictions
No full textAirlines experience schedule disruptions on a daily basis. Poor weather conditions, unscheduled aircraft maintenance and congested air spaces are just a few of the causes that prevent airlines from operating their flight schedules as planned. In the third quarter of 2017 over 20% of all scheduled flights in Europe suffered from delays. Operation Research based decision support systems (DSS) help airlines with their disruption management processes and provide suggestions for recovery options.For large hub-and-spoke carriers, with an extensive network and a large number of aircraft and flights, the computation time required to find the optimal recovery solution after a disruption increases rapidly. As airlines require fast recovery solutions when disruptions occur, there is an ongoing trade-off between computation time and system sophistication. In the majority of disruption cases, no or a limited number of undisrupted aircraft are required to find the optimal recovery solution. By selecting a limited number of aircraft, flights and airports used to find a recovery solution, the computation time is reduced exponentially. The challenge is determining which aircraft and flights should be selected.This research aims to develop a decision support system for the schedule and aircraft recovery process that is able to present a feasible solution to a disruption in less than 120 seconds. An aircraft recovery model will be developed based on the integer linear programming model that was created by Vink et al. (2019) and Vos et al. (2015). Crew and passenger recovery are not considered. To recover disruptions, the optimization model can delay and cancel flights as well as perform tails swaps, where the flights from two aircraft are switched. The novelty of the work is that machine learning is used to predict which undisrupted aircraft will help recover a disruption. Based on those predictions a sub-network selection algorithm will select the subset of aircraft to be included in the optimization instead of the entire aircraft fleet.The performance of the system is tested on a case study for the domestic hub-and-spoke network of Delta Airlines. The dataset for the study consists of 2200 daily flights, 147 airports and 827 aircraft in 8 aircraft families. The results of the system are compared with the optimal solution, where no aircraft selections were made. The case study shows that the system is able to make an aircraft selection where 50% of the fleet is discarded, while still finding the optimal solution in 98.9% of the 556 disruptions tested. Furthermore, the system reduces the computation time by 45%, resulting in an average time of 48 seconds. For the disruptions, the computation time varied between 9 and 180 seconds.Aerospace Engineerin
Two temperature generalized magneto-thermoelastic interactions in an elastic medium under three theories
No full textAbstractMagneto-thermoelastic interactions in an isotropic homogeneous elastic half-space with two temperatures are studied using mathematical methods under the purview of the Lord–Şhulman (LS) and Green–Lindsay (GL) theories, as well as the classical dynamical coupled theory (CD). The medium is considered to be permeated by a uniform magnetic field. The general solution obtained is applied to a specific problem of a half-space and the interaction with each other under the influence of magnetic field subjected to one types of heating the thermal shock type. The normal mode analysis is used to obtain the exact expressions for the displacement components, force stresses, temperature and couple stresses distribution. The variations of the considered variables through the horizontal distance are illustrated graphically. Comparisons are made with the results between the three theories. Numerical work is also performed for a suitable material with the aim of illustrating the results
Assessment of severity of bronchial asthma by studying new markers: transforming growth factor-β1 and chitinase-3-like-1
No full textAim
The aim of this work was to look for non-invasive biomarkers that may enable us to assess asthma severity, as a surrogate for the invasive bronchial mucosa biopsy, by studying TGF-β1 and YKL-40.
Objectives
TGF-β1 is used as biomarkers in the pathogenesis, prediction and follow up of asthma severity. YKL-40 has a role in airway inflammation; this relation suggests that YKL-40 and TGF-β1 can be used as biomarkers in the pathogenesis, prediction and follow-up of asthma severity.
Background
Defective extracellular matrix (ECM) turnover characterizes airway remodeling. Transforming Growth Factor Beta-1 (TGF-β1) stimulate airway remodeling through activation of gene transcription via binding to specific subfamilies of cell trans-membrane receptors.
Methods
The work was done on a 60 subject aged between 20–40 years with equal sex. Classified into three groups; 20 patients with mild asthma, 20 patients with severe asthma and 20 normal subjects were taken as controls. For all subjects chest X-ray, pulmonary functions tests, allergy skin prick test, eosinophilic count, total IgE, YKL-40 and TGF-β1 in serum were performed.
Results
The results showed that serum TGF-β1 and serum YKL-40 between the three groups were highly significantly different (P<0.01) between the three groups in asthmatic patients compared with control group.
Conclusions
These variations were correlated positively with the severity of the disease indicating that their increased serum levels may be a biological characteristic of the disease exacerbation with a sentinel role in asthma
URINARY LIVER TYPE-FATTY ACID BINDING PROTEIN AND PLASMA CYSTATIN C AS EARLY PREDICTORS OF CONTRAST INDUCED ACUTE KIDNEY INJURY
No full textEffect of early orthodontic force on shear bond strength of orthodontic brackets bonded with different adhesive systems
No full textTHE EFFECT OF HEPATITIS C VIRUS INFECTION ON INSULIN RESISTANCE IN CHRONIC HEMODIALYSIS PATIENTS
No full textA breast cancer classifier based on a combination of case-based reasoning and ontology approach
No full textThe elastic wave motions for a Photothermal medium of a dual-phase-lag model with an internal heat source and gravitational field
No full textIn this work, The dual-phase-lag (DPL) heat transfer model is introduced to study the problem of isotropic generalized thermoelastic medium with an internal heat source that is moving with a constant speed. Thermal loading at the free surface of a semi-infinite semiconconducting medium coupled plasma waves with the effect of mechanical force during a photothermal process to study the effect of the gravity field. The harmonic wave analysis is used to obtain the exact expressions for the considered variables, also the carrier density coefficient were obtained analytically. The variations of the considered variables through the horizontal distance are illustrated graphically under the effects of some several parameters based on the DPL model. The results are discussed and depicted graphically.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
Characterization of a gene common to cyanobacteria and higher plants ( psbH) and its possible function in photoinhibition
No full textThe psbH gene of the photosynthetic cyanobacterium, Synechocystis 6803, has been cloned from a EMBL 3 library of cyanobacterial chromosomal DNA. The gene is a single copy gene located on a 6.7 kb EcoRI fragment of the chromosomal DNA of Synechocystis 6803. Southern blot analysis and restriction mapping of the 6.7 kb fragment showed that an 0.8 kb fragment contains the coding sequence of the gene. DNA sequence analysis of this 0.8 kb fragment revealed a 70% sequence similarity to the corn psbH gene which was used as a probe. Computer analysis of this sequence revealed an open reading frame of 64 amino acids which had 64% sequence similarity to the corn psbH open reading frame. The phosphorylation site in the higher plant protein is known to be at the threonine residue at the third position in corn. The analogous Synechocystis 6803 gene is missing the first 12 amino acids from the N terminus corresponding to the corn protein, suggesting that the protein is not phosphorylated in Synechocystis 6803. An insertion mutation was created in the psbH gene of the Synechocystis 6803 by inserting a kanamycin resistance gene at the +21 base from the start codon. Photoinhibition studies showed that the presence of 30 mM sodium ascorbate during photoinhibition did not protect against photoinhibition, although 80% of the ascorbate added was in the reduced form after the photoinhibition. The light induced conversion of violaxanthin to zeaxanthin did not affect the thylakoid protein kinase activity. Both the treated sample (which had 7.8 mol zeaxanthin/100 mol chlorophyll a) and the control showed the same extent of phosphorylation. The presence of zeaxanthin during photoinhibition did not protect thylakoids against the photoinhibitory damage. The extent of photoinhibitory damage was similar in both the treatment which has light induced zeaxanthin formation (+Z) and the control (Z). (Abstract shortened with permission of author.
Global Buckling Analysis of Tapered Steel Members with Nonsymmetric Sections via an Updated-Lagrangian Line-Element Formulation
No full textWith the advancement in manufacturing technology, fabricating nonsymmetric steel sections by cold-forming or robotic welding is feasible, enabling innovative structural forms of being more structurally efficient. Nevertheless, members with nonsymmetric sections usually experience complex behaviour such as torsional, flexural-torsional, and lateral-torsional buckling, complicating their buckling strength prediction. The line-element method is proven efficient and robust for the stability analysis of framed structures. This paper develops a new tapered line-element suiting for nonlinear elastic buckling analysis of steel structures comprising tapered members with nonsymmetric sections. The approximate prediction of the varied cross-sectional properties along the length via the tapered variability indexes shows more accurate results than the stepped-element representation approach. Extensive parametric studies are conducted for the geometric parameters of typical shapes of nonsymmetric sections. The element tangent stiffness matrix, compatible with the existing frame analysis programs, is derived via the total potential energy principle. Moreover, the numerical procedure of the proposed method via the Updated-Lagrangian (UL) approach is elaborated and validated through several benchmark examples generated by shell-finite elements. Finally, the practical application of the proposed method is explored. This paper provides a new line element for a nonlinear elastic analysis to examine global buckling behaviours that represent an initial basis for forthcoming nonlinear collapse simulations with imperfections that are the primary goals in future studies.The first author would like to acknowledge the financial support from the Competitive Research Projects, Postgraduate, Research, and Cultural Affairs Sector, Mansoura University, Egypt
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