1,474 research outputs found
Influence of temperature and sliding speed on the subsurface microstructure evolution of EN AW-6060 under sticking friction conditions
No full textThis article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in AIP Conference Proceedings 1896, 140012 (2017) and may be found at https://doi.org/10.1063/1.5008168.The microstructure evolution of the friction boundary layer of the aluminum alloy EN AW-6060 was investigated. Sticking friction tests at different temperatures and sliding speeds were carried out. A severe deformation below the friction surface was observed by means of LOM and EBSD mapping. Thus, the thickness variation and the grain structure of the high deformation zone could be described. Fibrous structure was observed at 300 °C and 400 °C, while equiaxed grains with high misorientation angle (>15°) were generated at higher temperatures. Additionally, abnormal grain growth and coarse grains were detected at high sliding speeds (10 mm/s, 42 mm/s) at 450°C and 500 °C respectively
Author-Suggested, Weighted Citation Index: A Novel Approach for Determining the Contribution of Individual Researchers
No full textA novel scientometric index, named ‘author-suggested, weighted citation index’ (Aw-index) is proposed to indicate the scientific contribution of any individual researcher. For calculation of the Aw-index, it is suggested that during the submission of a scholarly article, the corresponding author would provide a statement, agreed upon by all the authors, containing weightage factors against each author of the article. The author who contributed more to the article would secure a higher weightage factor. The summation of the weightage factors of all the authors of an article should be unity. The citation points a researcher receives from a scholarly publication is the product of his/her weightage factor for that article and the total number of citations of the article. The Aw-index of any individual researcher is the summation of the citation points he/she receives for all his/her publications as an author. The Aw-index provides the opportunity to the group of authors of a multi-authored article to determine the quantum of partial citations to be attributed to each of them. Through an illustrative example, a comparison of the proposed index with the major scientometric indexes is presented to highlight the advantages of the Aw-index
Influence of Process Parameters on the Quality of Aluminium Alloy EN AW 7075 Using Selective Laser Melting (SLM)
No full textAbstractSelective laser melting (SLM) is an additive manufacturing process, forming the desired geometry by selective layer fusion of powder material. Unlike conventional manufacturing processes, highly complex parts can be manufactured with high accuracy and little post processing. Currently, different steel, aluminium, titanium and nickel-based alloys have been successfully processed; however, high strength aluminium alloy EN AW 7075 has not been processed with satisfying quality. The main focus of the investigation is to develop the SLM process for the wide used aluminium alloy EN AW 7075. Before process development, the gas-atomized powder material was characterized in terms of statistical distribution: size and shape. A wide range of process parameters were selected to optimize the process in terms of optimum volume density. The investigations resulted in a relative density of over 99%. However, all laser-melted parts exhibit hot cracks which typically appear in aluminium alloy EN AW 7075 during the welding process. Furthermore the influence of processing parameters on the chemical composition of the selected alloy was determined
Zhedanov's Algebra AW(3) and the Double Affine Hecke Algebra in the Rank One Case. II. The Spherical Subalgebra
No full textThis paper builds on the previous paper by the author, where a relationship between Zhedanov's algebra AW(3) and the double affine Hecke algebra (DAHA) corresponding to the Askey-Wilson polynomials was established. It is shown here that the spherical subalgebra of this DAHA is isomorphic to AW(3) with an additional relation that the Casimir operator equals an explicit constant. A similar result with q-shifted parameters holds for the antispherical subalgebra. Some theorems on centralizers and centers for the algebras under consideration will finally be proved as corollaries of the characterization of the spherical and antispherical subalgebra
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Extensions and amplifications of a traffic model of Aw and Rascle
No full textIn a recent paper [1] Aw and Rascle introduced a new model of traffic on a uni-directional highway. Here the author studies an extension of this model, one which accounts for drivers attempting to travel at their maximum allowable speed. The author looks at a Lagrangian reformulation of this problem; a formulation that leads to an effective computational algorithm for solving the resulting system. He also investigates approximation scheme introduced by Dafermos [5] for scalar conservation laws and demonstrates that this Dafermos scheme works well on this 2 x 2 system
Automating the determination of wave speed using the pu-loop method
No full textThe PU-loop (pressure-velocity loop) is a method for determining wave speed and relies on the linear relationship between the pressure and velocity in the absence of reflected waves. This linearity of the PU-loop during early systole, which is directly related to wave speed, has always been established by eye. This paper presents a new technique that establishes this linearity and thus determining wave speed online. Pressure and flow were measured in the ascending aorta of 11 anesthetised dogs. The slope of the PU-loop, indicating wave speed was determined by eye and by using the new technique. The difference between the slopes of the two methods is in the order of 3%. The new technique is convenient and allows for the online assessment of wave speed, which could be used as a bedside tool for the assessment of arterial compliance
Simultaneous three-dimensional printing and frontal polymerization of dicyclopentadiene resin
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Previous issue date: 2019-04-26Three-dimensional (3D) printing has widespread uses across many industries due to its versatility and capabilities. However, freeform fabrication of thermoset polymers remains a technical challenge. This thesis combines 3D printing with frontal polymerization (FP) — a method to rapidly cure resin — for curing filaments in tandem with the printing process. A partially cured dicyclopentadiene (DCPD) resin was developed into a printing ink. Critical rheological characteristics were identified, and DCPD inks of varying incubation times were screened to find the most suitable properties. Results of the rheological study indicate that 90 minutes of incubation time resulted in optimum print behavior. Problems associated with FP were effectively tackled through temperature control across the printing setup. In situ infrared images showed an exothermic reaction front propagating during the print process, giving evidence of in situ polymerization. The optimized technique produced one-dimensional, two-dimensional and 3D freeform prints with excellent fidelity. A self-equilibrating behavior was identified in the reaction front, such that the front autonomously tune its speed to the programmed print speed. This phenomenon autonomously controls the viscoelastic bridge length, Lb, and inevitably curbs deformations to achieve high print fidelity.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2021-05-01The student, Jia En Aw, accepted the attached license on 2019-04-26 at 14:07.The student, Jia En Aw, submitted this Thesis for approval on 2019-04-26 at 14:16.This Thesis was approved for publication on 2019-04-26 at 14:46.DSpace SAF Submission Ingestion Package generated from Vireo submission #13952 on 2019-08-22 at 16:24:04Embargo set by: Seth Robbins for item 112399
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Cerebrospinal fluid flow quantification in the brain using magnetic resonance imaging
No full textHydrocephalus is a severe brain condition in which cerebrospinal fluid (CSF) cannot properly drain into the spinal cord, resulting in a buildup of pressure. To relieve this pressure, a shunt is placed in the brain that drains the CSF. However, the failure rate of these shunts is high, requiring additional surgeries to check functionality or for replacement. As this is costly and invasive, a way to quantitatively measure the shunt flow without surgery would be valuable. In this work, we modify a previously successful technique that quantified blood flow in the brain to quantify CSF flow. This technique, called flow enhanced signal intensity (FENSI), uses magnetic resonance (MR) to gain a quick and accurate measurement. By adjusting imaging parameters from quantitative FENSI (qFENSI), we can optimize this sequence to be sensitive to CSF flow. We demonstrate the sensitivity of our technique down to 0.1 ml/min and up to 0.4 ml/min. Additionally, taking into account the T1 relaxation rate, we can fit a curve to the data points using simulations to predict the flow rate of the measured signal.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2021-05-01The student, Natalie Aw, accepted the attached license on 2019-04-11 at 12:55.The student, Natalie Aw, submitted this Thesis for approval on 2019-04-12 at 12:21.This Thesis was approved for publication on 2019-04-12 at 13:59.DSpace SAF Submission Ingestion Package generated from Vireo submission #13565 on 2019-08-22 at 15:05:53Made available in DSpace on 2019-08-23T20:35:50Z (GMT). No. of bitstreams: 2
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Previous issue date: 2019-04-12Embargo set by: Seth Robbins for item 112124
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Improved Numerical Method for Aw-Rascle Type Continuum Traffic Flow Models
No full textContinuum traffic flow models are essentially nonlinear hyperbolic systems of partial differential equations. Except for limited specific cases, these systems must be solved numerically. Mathematical structure of continuum models can be different for each class of models. As a result, suitable numerical schemes for some classes may not be efficient for others. In this study, an improved numerical method is proposed for a class of second-order traffic flow models. The method is based on McCormack scheme, which is a widely-used method for non-homogeneous second-order traffic flow models, but fails to produce reasonable results for homogeneous models including Aw-Rascle type models which are the focus of this paper. It is shown that this is mainly due to spurious numerical oscillations. Smoothing methods to overcome these issues are studied and applied. Central dispersion and artificial viscosity (AV) methods are incorporated into the standard McCormack scheme and tested. To reduce numerical diffusion, a total variation diminishing Runge-Kutta time stepping scheme is applied. Results show the capability of the proposed methods, and especially the AV method, to eliminate the oscillations of the standard McCormack scheme as well as controlling numerical diffusion.Transport and Plannin
Natronobiforma cellulositropha gen. nov., sp. nov., a novel haloalkaliphilic member of the family Natrialbaceae (class Halobacteria) from hypersaline alkaline lakes
No full textSix strains of extremely halophilic and alkaliphilic euryarchaea were enriched and isolated in pure culture from surface brines and sediments of hypersaline alkaline lakes in various geographical locations with various forms of insoluble cellulose as growth substrate. The cells are mostly flat motile rods with a thin monolayer cell wall while growing on cellobiose. In contrast, the cells growing with cellulose are mostly nonmotile cocci covered with a thick external EPS layer. The isolates, designated AArcel, are obligate aerobic heterotrophs with a narrow substrate spectrum. All strains can use insoluble celluloses, cellobiose, a few soluble glucans and xylan as their carbon and energy source. They are extreme halophiles, growing within the range from 2.5 to 4.8 M total Na+ (optimum at 4 M) and obligate alkaliphiles, with the pH range for growth from 7.5 to 9.9 (optimum at 8.5–9). The core archaeal lipids of strain AArcel5T were dominated by C20–C20 dialkyl glycerol ether (DGE) (i.e. archaeol) and C20–C25 DGE in nearly equal proportion. The 16S rRNA gene analysis indicated that all six isolates belong to a single genomic species mostly related to the genera Saliphagus-Natribaculum-Halovarius. Taking together a substantial phenotypic difference of the new isolates from the closest relatives and the phylogenetic distance, it is concluded that the AArcel group represents a novel genus-level branch within the family Natrialbaceae for which the name Natronobiforma cellulositropha gen. nov., sp. nov. is proposed with AArcel5T as the type strain (JCM 31939T = UNIQEM U972T).doi 10.1016/j.syapm.2018.11.007 contains this corrigendum: 1. The species name “cellulotropha” was corrected to “cellulositropha” in the (SPNA), (SPEP) and TITL lines. 2. The author name “Damstéd” in the (AUT) was corrected to “Damsté”. 3.The word “neutral” in the (GETY/SPTY) was corrected to “neut”. 4.Some of the relevant values have been added to both genus and species columns.BT/Environmental Biotechnolog
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