35,493 research outputs found
Constructal design of pedestrian evacuation from an area
No full textAuthor name used in this publication: Lui, C. H.Author name used in this publication: Fong, N. K.Author name used in this publication: Chow, W. K.2012-2013 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishedVoR allowe
Robust Rank Preservation of Matrices with Both Structured and Unstructured Uncertainties and Its Applications
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Metastable Innershell Molecular State (MIMS) IV: Heteronucleus K-shell MIMS with H+ and He+
No full textAbstractThe model of MIMS (Metastable Innershell Molecular State) has been applied to interpreting the Kα X-ray satellite data of target atoms in H+ and He+ ion impact on Al, Ca and Ti targets. The binding energies of the heteronucleus H-K-MIMS (K-shell MIMS formed with H and a target atom) and He-K-MIMS have been obtained. The binding energy trend of the H-K-MIMS shows a Z2 dependency similar to that of the homonucleus K-MIMS, while that of the He-K-MIMS shows a transitional behavior from the former to the latter. These behaviors were interpreted with the Z-expansion theory of heteronucleus molecules
Comparison of several author indices for gauging academic productivity
No full textBackground
Many author indices exist to gauge academic productivity. Several of these indices are calculated based upon an author's scholarly publication record, but the measurement methodology to calculate each index varies considerably, and the precise function being used, as well as the end result, is often complex and difficult to assess.
Method
Two straightforward methods to weigh author productivity from the publication and citation record were evaluated as possible means for providing a clearer assessment of scholarly activity. The author characteristic index (termed c-index) assigns author rank for each publication based upon author position. The characteristic prime (c') -index normalizes author rank from author position, so that the total weight per publication is unity. The top 10 scholars with keyword 'celiac disease' in the Google Scholar database were then assessed using these metrics. Rankings according to total number of publications, h-index, and c- and c'-indices were compared, then tabulated along with total papers included for assessment, and mean values per paper for author position, number of authors, citations, and year of publication.
Results
The order of the top ten authors with keyword 'celiac disease' varied substantially depending upon whether the h-index, c-index, or c'-index was used as a gauge. The characteristic indices assign credit to authors according to their position in an author list. The affiliated metrics provided a more complete picture of scholarly activity.
Conclusions
Academic achievement by scholars, based upon quantitative publication characteristics, has recently become of interest for evaluating job candidates, for determining work performance, and for bestowing awards and honors. The characteristic indices as described herein are readily calculated and interpreted, and may improve the assessment of scholarly activity
Fatigue and Fracture behaviour of AZ31b Mg alloy plastically deformed by Constrained Groove Pressing in the Presence of Overloads
No full textWithin the class of lightweight metallic materials, magnesium alloys are gaining popularity mainly thanks to abundant supply and high specific strength. A weakness of Mg alloys is their poor formability at room temperature. For this reason, in recent years thermo-mechanical treatments have often been sought that would improve this aspect. One particular way towards the combination of better formability (ductility) and strength is through grain refinement by means of Constrained Groove Pressing (CGP). The use of a pair of matching dice having groove-like geometry, coupled with controlled process temperature, allows promoting microstructural refinement and achieving sub-micron grain size in the processed plates. The purpose of the present study was to characterise the resulting fine-grained material in plate form in terms its fatigue fracture behaviour. Compact tension samples were machined and subjected to cyclic tensile loading to monitor fracture propagation and extract their Fatigue Crack Growth Rate (FCGR) behaviour as a function of the applied crack tip Stress Intensity Factor range. Firstly, as a reference sample an as-received material plate was tested at the loading ratio R=0.1. Subsequently, CGP-processed fine-grained material was tested at R=0.1 and R=0.7, and subjected to anomalous load that included overload (50% increase in the maximum load) and, in the specific case of R=0.1, underload (reversal of the sign of minimum load from tension to compression). These studies provided the critically needed input for the development of new approaches to the evaluation of the apparent fracture resistance of the material processed by CGP under variable amplitude loading (i.e. overload and underload) essential for accurate fatigue life prediction for a broad variety of applications. By combining the Walker model accounting for the mean stress effect and a modified Wheeler model for crack growth retardation due to the application of a single overload, a new predictive approach was formulated
Direct optical transitions at K- and H-point of Brillouin zone in bulk MoS2, MoSe2, WS2, and WSe2
No full textabstract: Modulated reflectance (contactless electroreflectance (CER), photoreflectance (PR), and piezoreflectance (PzR)) has been applied to study direct optical transitions in bulk MoS[subscript 2], MoSe[subscript 2], WS[subscript 2], and WSe[subscript 2]. In order to interpret optical transitions observed in CER, PR, and PzR spectra, the electronic band structure for the four crystals has been calculated from the first principles within the density functional theory for various points of Brillouin zone including K and H points. It is clearly shown that the electronic band structure at H point of Brillouin zone is very symmetric and similar to the electronic band structure at K point, and therefore, direct optical transitions at H point should be expected in modulated reflectance spectra besides the direct optical transitions at the K point of Brillouin zone. This prediction is confirmed by experimental studies of the electronic band structure of MoS[subscript 2], MoSe[subscript 2], WS[subscript 2], and WSe[subscript 2] crystals by CER, PR, and PzR spectroscopy, i.e., techniques which are very sensitive to critical points of Brillouin zone. For the four crystals besides the A transition at K point, an A[subscript H] transition at H point has been observed in CER, PR, and PzR spectra a few tens of meV above the A transition. The spectral difference between A and A[subscript H] transition has been found to be in a very good agreement with theoretical predictions. The second transition at the H point of Brillouin zone (B[subscript H] transition) overlaps spectrally with the B transition at K point because of small energy differences in the valence (conduction) band positions at H and K points. Therefore, an extra resonance which could be related to the B[subscript H] transition is not resolved in modulated reflectance spectra at room temperature for the four crystals.This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in Journal of Applied Physics and may be found at http://aip.scitation.org/doi/10.1063/1.4954157
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