The existing literature review articles in composite materials research field target a particular resin material which cannot show the full picture of the research area. The traditional literature ...reviews are vulnerable to subjective opinion on selecting, reviewing and analyzing the related articles. In this systematic literature review, keywords were input into Web of Science (WOS) search engine to collect relevant articles from the database. This method can more comprehensively review articles that are related to fiber-reinforced polymer composites. Articles published from 1970 to 2020 were collected from the WOS database. Keywords input were relevant to manufacturing, enhancement and sustainability of fiber-reinforced polymer composites and their variants. 151 articles were selected based on keyword filtering, nature of articles and content, and further examined with citation network analysis. Seven principal clusters were formed and evaluated. Publication year, geographical locations, research areas and journal of the selected articles were presented statistically. Two major clusters, “fabrication and molding methods of composites” and “properties and performance of multiscale composites”, were identified and a few emerging clusters were found to establish their networks including topics about impact response, natural fiber, rapid curing, nanofiller, and hydrothermal aging. Future research and more results are needed in those emerging clusters.
Abstract
A number of studies based on the data collected by the Hubble Space Telescope (HST) GO-13297 program “HST Legacy Survey of Galactic Globular Clusters: Shedding UV Light on Their Populations ...and Formation” have investigated the photometric properties of a large sample of Galactic globular clusters and revolutionized our understanding of their stellar populations. In this paper, we expand upon previous studies by focusing our attention on the stellar clusters’ internal kinematics. We computed proper motions for stars in 56 globular clusters and one open cluster by combining the GO-13297 images with archival HST data. The astrophotometric catalogs released with this paper represent the most complete and homogeneous collection of proper motions of stars in the cores of stellar clusters to date, and expand the information provided by the current (and future) Gaia data releases to much fainter stars and into the crowded central regions. We also census the general kinematic properties of stellar clusters by computing the velocity dispersion and anisotropy radial profiles of their bright members. We study the dependence on concentration and relaxation time, and derive dynamical distances. Finally, we present an in-depth kinematic analysis of the globular cluster NGC 5904.
We use 14 orbits of Advanced Camera for Surveys observations to reach the end of the white dwarf cooling sequence in the globular cluster M4. Our photometry and completeness tests show that the end ...is located at magnitude m F606W = 28.5 - 0.1, which implies an age of 11.6 - 0.6 Gyr (internal errors only). This is consistent with the age from fits to the main-sequence turnoff (12.0 - 1.4 Gyr).
We present new observations of the white dwarf sequence of the old open cluster NGC 6791. The brighter peak previously observed in the white dwarf luminosity function (WDLF) is now better delineated, ...and the second, fainter peak that we suggested earlier is now confirmed. A careful study suggests that we have reached the end of the WD sequence. The WDs that create the two peaks in the WDLF show a significant turn to the blue in the color-magnitude diagram. The discrepancy between the age from the WDs and that from the main- sequence turnoff remains, and we have an additional puzzle in the second peak in the WDLF. Canonical WD models seem to fail-at least at image25% level-in reproducing the age of clusters of this metallicity. We discuss briefly possible ways of arriving at a theoretical understanding of the WDLF.
Having shown in a recent paper that the main sequence of omega Centauri is split into two distinct branches, we now present spectroscopic results showing that the bluer sequence is less metal-poor. ...We have carefully combined VLT's GIRAFFE spectra of 17 stars on each side of the split into a single spectrum for each branch, with adequate signal-to-noise ratio, to show clearly that the stars of the blue main sequence are less metal-poor by 0.3 dex than those of the dominant red one. From an analysis of the individual spectra, we could not detect any abundance spread among the blue main-sequence stars, whereas the red main-sequence stars show a 0.2 dex spread in metallicity. We use stellar structure models to show that only greatly enhanced helium can explain the color difference between the two main sequences, and we discuss ways in which this enhancement could have arisen.
As part of the ACS Survey of Galactic Globular Clusters, we present new Hubble Space Telescope photometry of the massive globular cluster M54 (NGC 6715) and the superposed core of the tidally ...disrupted Sagittarius (Sgr) dSph galaxy. Our deep (F606W 6 26.5), high-precision photometry yields an unprecedentedly detailed color-magnitude diagram showing the extended blue horizontal branch and multiple main sequences of the M54+Sgr system. The distance and reddening to M54 are revised using both isochrone and main-sequence fitting to (m - M)(0) = 17.27 and E(B V) = 0.15. preliminary assessment finds the M54+Sgr field to be dominated by the old metal-poor populations of Sgr and the globular cluster. Multiple turnoffs Indicate the presence of at least two intermediate-aged star formation epochs with 4 and 6 Gyr ages and Fe/H = -0.4 (t0) _0.6. We also clearly show, for the first time, a prominent, 62.3 Gyr old Sgr population of near-solar abundance. A trace population of even younger (60.1-0.8 Gyr old), more metal-rich (Fe/H 6 0.6) stars is also indicated. The Sgr age-metallicity relation is consistent with a closed-box model and multiple (4-5) star formation bursts over the entire life of the satellite, including the time since Sgr began disrupting.
The first step toward doing high‐precision astrometry is the measurement of individual stars in individual images, a step that is fraught with dangers when the images are undersampled. The key to ...avoiding systematic positional error in undersampled images is to determine an extremely accurate point‐spread function (PSF). We apply the concept of theeffectivePSF (ePSF) and show that in images that consist of pixels it is the ePSF, rather than the often‐used instrumental PSF, that embodies the information from which accurate star positions and magnitudes can be derived. We show how, in a rich star field, one can use the information from dithered exposures to derive an extremely accurate effective PSF by iterating between the PSF itself and the star positions that we measure with it. We also give a simple but effective procedure for representing spatial variations of theHubble Space TelescopePSF. With such attention to the PSF, we find that we are able to measure the position of a single reasonably bright star in a single image with a precision of 0.02 pixel (2 mas in WF frames, 1 mas in PC), but with a systematic accuracy better than 0.002 pixel (0.2 mas in WF, 0.1 mas in PC), so that multiple observations can reliably be combined to improve the accuracy by
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