This is the first detailed study on the coverage of Microsoft Academic (MA). Based on the complete and verified publication list of a university, the coverage of MA was assessed and compared with two ...benchmark databases, Scopus and Web of Science (WoS), on the level of individual publications. Citation counts were analyzed, and issues related to data retrieval and data quality were examined. A Perl script was written to retrieve metadata from MA based on publication titles. The script is freely available on GitHub. We find that MA covers journal articles, working papers, and conference items to a substantial extent and indexes more document types than the benchmark databases (e.g., working papers, dissertations). MA clearly surpasses Scopus and WoS in covering book-related document types and conference items but falls slightly behind Scopus in journal articles. The coverage of MA is favorable for evaluative bibliometrics in most research fields, including economics/business, computer/information sciences, and mathematics. However, MA shows biases similar to Scopus and WoS with regard to the coverage of the humanities, non-English publications, and open-access publications. Rank correlations of citation counts are high between MA and the benchmark databases. We find that the publication year is correct for 89.5% of all publications and the number of authors is correct for 95.1% of the journal articles. Given the fast and ongoing development of MA, we conclude that MA is on the verge of becoming a bibliometric superpower. However, comprehensive studies on the quality of MA metadata are still lacking.
TEM investigations of dislocation structures in core and surface regions (50
μm below the free surface) were carried out on polycrystalline nickel samples of 500
μm thickness with 14, 2.5 and 1 grain ...across the thickness. The mean diameter of the dislocation cells was measured for different strain levels in core and surface regions of the three kinds of sample. These mean dislocation cell diameters were compared between the different samples using a statistical analysis of variance. The intragranular long-range internal backstress level was thereafter estimated in both regions for the three samples revealing a decrease in stress for specimens with few grains across the thickness. This decrease is partially responsible for the flow stress decrease of the nickel polycrystals with few grains across the thickness.
If the grain size reduction is known to enhance the yield stress of alloys, its impact on the corrosion resistance is still misunderstood. In this work, corrosion and passivation mechanisms of ...stainless steel 316L manufactured by ball milling and spark plasma sintering were studied in Na2SO4. The elaboration by powder metallurgy and fast sintering route produces dense samples with grain sizes in the ultrafine domain without crystallographic texture. Electrochemical properties were analysed by potentiodynamic polarization experiments. The samples display weak passivation current density, typically around a few μA/cm2, with a grain size reduction. This was related to an increase in polarization resistance of the free surfaces for smallest grain sizes. Moreover, a passivation of the milled powder in HNO3 before sintering has a beneficial impact on the stability of the passive layer, especially for the smallest grain sizes. The physical properties of the oxide layer were analysed by impedance spectroscopy and Mott-Schottky formalism. Capacitive properties and thickness of the oxide do not strongly depend of the grain size. Smallest grain size specimens manufactured with passivated powder exhibit the higher electrical resistance of the interface. Donor density also decreases with grain size, leading to most compact and less defective oxide layer.
Display omitted
•Stainless steels 316L were manufactured by ball milling and Spark Plasma sintering.•High density samples with grain sizes in the ultrafine domain and no texture were obtained.•Decreasing grain size enhances the passivation properties of 316L in neutral electrolyte.•Passivation of the powder before sintering has a beneficial impact on the stability of the passive layer.
In this paper the influence of varying the starting conditions on intensity-modulated proton therapy (IMPT) plans has been studied. In particular IMPT plans have been optimized based on four ...different starting conditions of initial beamlet fluences: (a) all beamlets with an initial constant weight, delivering a gradient from the proximal to the distal edge of the target (forward wedge approach); (b) beamlet weights reduced from the distal to the proximal aspect of the target such as to deliver a flat 'spread-out-Bragg-peak' (SOBP approach); (c) beamlet weights calculated to deliver a gradient from the distal (maximal dose) to the proximal edge (inverse wedge); (d) beamlet weights set universally to zero except the most distal one, for each given lateral direction (i.e. distal-edge-tracking, DET). An analysis of robustness to range errors has been performed by recalculating plans, assuming a systematic 3% error in CT values. Results showed that IMPT plans optimized with the forward wedge approach were very sensitive to range errors, since organs-at-risk (OAR) were spared by patching single-field lateral and distal fall-offs, the last ones being strongly sensitive to range errors. In addition a plan robust to range errors can be achieved by starting the optimization process in the case of low-dose constraints to OAR, with the initial flat SOBP approach, and with either the DET or the inverse wedge approaches, in the case of stringent dose-volume constraints to OAR. 'Starting condition-based optimization' as proposed here can therefore provide a tool to transparently 'steer' the optimization outcome to solutions more robust to uncertainties.
Local tumor control, patient survival, and treatment failure outcomes were analyzed to assess treatment efficacy in 58 patients in whom fractionated proton radiation therapy (RT) was administered for ...skull base chordomas and chondrosarcomas.
Between March 1992 and January 1998, a total of 58 patients who could be evaluated were treated for skull base tumors, 33 for chordoma and 25 for chondrosarcoma. Following various surgical procedures, residual tumor was detected in 91% of patients; 59% demonstrated brainstem involvement. Target dosages ranged from 64.8 and 79.2 (mean 70.7) Co Gy equivalent. The range of follow up was 7 to 75 months (mean 33 months). In 10 patients (17%) the treatment failed locally, resulting in local control rates of 92% (23 of 25 patients) for chondrosarcomas and 76% (25 of 33 patients) for chordomas. Tumor volume and brainstem involvement influenced control rates. All tumors with volumes of 25 ml or less remained locally controlled, compared with 56% of tumors larger than 25 ml (p = 0.02); 94% of patients without brainstem involvement did not experience recurrence; in patients with brainstem involvement (and dose reduction because of brainstem tolerance constraints) the authors achieved a tumor control rate of 53% (p = 0.04). Three patients died of their disease, and one died of intercurrent disease. Actuarial 5-year survival rates were 100% for patients with chondrosarcoma and 79% for patients with chordoma. Grade 3 and 4 late toxicities were observed in four patients (7%) and were symptomatic in three (5%).
High-dose proton RT offers excellent chances of lasting tumor control and survival, with acceptable risks. In this series all small- and medium-sized tumors with no demonstrable brainstem involvement have been controlled; all such patients are alive. Surgical debulking enhanced delivery of full tumoricidal doses, but even patients with large tumors and disease abutting crucial normal structures benefited.
Towards theorizing peer review Hug, Sven E.
Quantitative science studies,
11/2022, Letnik:
3, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Academic peer review is seriously undertheorized because peer review studies focus on discovering and confirming phenomena, such as biases, and are much less concerned with explaining, predicting, or ...controlling phenomena on a theoretical basis. In this paper, I therefore advocate for more theorizing in research on peer review. I first describe the main characteristics of the peer review literature, which focuses mainly on journal and grant peer review. Based on these characteristics, I then argue why theory is useful in research on peer review, and I present some theoretical efforts on peer review. I conclude by encouraging peer review researchers to be more theoretically engaged and outline activities that theoretical work on peer review could involve. This invitation to theory-building complements recent roadmaps and calls that have emphasized that we need to have better access to peer review data, improve research design and statistical analysis in peer review studies, experiment with innovative approaches to peer review, and provide more funding for peer review research.
The thermomechanical behavior of polycrystalline sheets of high purity copper with various numbers of grains (d) across the thickness (t) is experimentally analyzed. As for other face centered cubic ...materials, the t/d ratio strongly affects the work hardening of copper, especially for t/d values lower than a critical one around five. These results are in agreement with previous ones concerning nickel and can be correlated with surface effects which progressively take place in the material when few grains are present across the thickness. The t/d ratio mainly affects the second work hardening stage and an increase in temperature tends to reduce this effect due to the early beginning of cross slip which leads to a generalization of the surface properties on the overall volume of the material. This result is supported by the analysis of the dislocation structures during the second and third hardening stages for polycrystalline and multicrystalline specimens. As a consequence, the forming of thin metallic products should be ideally performed at moderate temperatures in order to avoid size effects which can deteriorate the reliability of the final product.
•The influence of temperature on the size effects in some fcc polycrystals is reported.•High stacking fault energy polycrystals always behave differently than multicrystals.•Work hardening of low ...stacking fault energy polycrystals tends toward multicrystals one.•Surface effects and grain size influence can be successfully dissociated.•Formability of thin parts can be optimized by appropriate strain paths and temperature.
The mechanical behavior of face centered cubic metals is deeply affected when specimen dimensions decrease from a few millimeters to a few micrometers. At room temperature, a critical thickness (t) to grain size (d) ratio (t/d)c was previously highlighted, under which the softening of mechanical properties became very pronounced both in terms of Hall–Petch relation and work hardening mechanisms. In this work, new experimental results are provided concerning the influence of temperature on this size effect for copper, nickel and Ni–20wt.%Cr, representative of a wide range of deformation mechanisms (i.e. dislocation slip character). It is shown that multicrystalline samples (t/d<(t/d)c) are not deeply affected by an increase in temperature, independently of the planar or wavy character of dislocation glide. For pronounced wavy slip character metals, surface effects in polycrystals (t/d>(t/d)c) are not significant enough to reduce the gap between polycrystal and multicrystal mechanical behavior when the temperature increases. However, a transition from wavy slip to planar glide mechanisms induces a modification of the polycrystalline behavior which tends toward multicrystalline one with a moderate increase in temperature. This work demonstrates that surface effects and grain size influence can be successfully disassociated for the three studied materials using an analysis supported by the Kocks–Mecking formalism. All these results are supported by microscopic investigations of dislocation substructures and compared to numerical simulations using a strain gradient plasticity model.
We explore if and how Microsoft Academic (MA) could be used for bibliometric analyses. First, we examine the Academic Knowledge API (AK API), an interface to access MA data, and compare it to Google ...Scholar (GS). Second, we perform a comparative citation analysis of researchers by normalizing data from MA and Scopus. We find that MA offers structured and rich metadata, which facilitates data retrieval, handling and processing. In addition, the AK API allows retrieving frequency distributions of citations. We consider these features to be a major advantage of MA over GS. However, we identify four main limitations regarding the available metadata. First, MA does not provide the document type of a publication. Second, the “fields of study” are dynamic, too specific and field hierarchies are incoherent. Third, some publications are assigned to incorrect years. Fourth, the metadata of some publications did not include all authors. Nevertheless, we show that an average-based indicator (i.e. the journal normalized citation score; JNCS) as well as a distribution-based indicator (i.e. percentile rank classes; PR classes) can be calculated with relative ease using MA. Hence, normalization of citation counts is feasible with MA. The citation analyses in MA and Scopus yield uniform results. The JNCS and the PR classes are similar in both databases, and, as a consequence, the evaluation of the researchers’ publication impact is congruent in MA and Scopus. Given the fast development in the last year, we postulate that MA has the potential to be used for full-fledged bibliometric analyses.
•Softening of mechanical behavior due to miniaturization is analyzed.•Different stress paths are employed.•Hall–Petch relationship is investigated for different stress paths.•Results show that the ...miniaturization softening is linked to triaxiality.
The mechanical behavior of metallic materials deeply depends on the size of samples. For specimen dimensions decreasing from a few millimeters to a few micrometers, the general observed trend is a softening of the mechanical behavior in tension which affects the stress level and the strain hardening. The objective of this work is to provide new experimental results in order to analyze the miniaturization size effects for various stress paths without strain gradients across the thickness of the samples. To this aim, experimental tensile tests, large tensile tests and shear tests have been performed on Ni sheets with various grain sizes. Results show that the miniaturization softening is affected by triaxiality, the larger is this parameter, the lower is the mechanical softening. These features seem to be linked to surface effects which are larger for low triaxiality stress paths. From an industrial point of view, it is hence possible to improve the forming of microparts using suitable stress paths.
PDF
