Automated Defect Detection and Characterization on Pulse Thermography Images Using Computer Vision Techniques

Defect detection and characterization plays a vital role in predicting the life span of materials. Defect detection using appropriate inspection technologies at various phases has gained huge importance in metal production lines. It can be accomplished through wise application of non-destructive testing and evaluation (NDE). It is important to characterize defects at an early stage in order to be able to overcome them or take corrective measures. Pulse thermography is a modern NDE method that can be used for defect detection in metal objects. Only a limited amount of work has been done on automated detection and characterization of defects due to thermal diffusion. This paper proposes a system for automatic defect detection and characterization in metal objects using pulse thermography images as well as various image processing algorithms and mathematical tools. An experiment was carried out using a sequence of 250 pulse thermography images of an AISI 316 L stainless steel sheet with synthetic defects. The proposed system was able to detect and characterize defects sized 10 mm, 8 mm, 6 mm, 4 mm and 2 mm with an average accuracy of 96%, 95%, 84%, 77%, 54% respectively. The proposed technique helps in the effective and efficient characterization of defects in metal objects

Numerical solution on thermal radiation with unsteady MHD flow

Abstract The numerical study on unsteady MHD flow in a porous medium through past a vertical porous plate. The governing equation of flow field used by Crank-Nicolson finite difference method. Under thermal radiation only,showing the figures temperature for different values of function, parameter (v 0 ) and prandtl number (P r )

Polarization studies of Rotating Radio Transients

We study the polarization properties of 22 known rotating radio transients (RRATs) with the 64-m Parkes radio telescope and present the Faraday rotation measures (RMs) for the 17 with linearly polarized flux exceeding the off-pulse noise by 3$\sigma$. Each RM was estimated using a brute-force search over trial RMs that spanned the maximum measurable range $\pm1.18 \times 10^5 \, \mathrm{rad \, m^2}$ (in steps of 1 $\mathrm{rad \, m^2}$), followed by an iterative refinement algorithm. The measured RRAT RMs are in the range |RM| $\sim 1$ to $\sim 950$ rad m$^{-2}$ with an average linear polarization fraction of $\sim 40$ per cent. Individual single pulses are observed to be up to 100 per cent linearly polarized. The RMs of the RRATs and the corresponding inferred average magnetic fields (parallel to the line-of-sight and weighted by the free electron density) are observed to be consistent with the Galactic plane pulsar population. Faraday rotation analyses are typically performed on accumulated pulsar data, for which hundreds to thousands of pulses have been integrated, rather than on individual pulses. Therefore, we verified the iterative refinement algorithm by performing Monte Carlo simulations of artificial single pulses over a wide range of S/N and RM. At and above a S/N of 17 in linearly polarized flux, the iterative refinement recovers the simulated RM value 100 per cent of the time with a typical mean uncertainty of $\sim5$ rad m$^{-2}$. The method described and validated here has also been successfully used to determine reliable RMs of several fast radio bursts (FRBs) discovered at Parkes.Comment: Submitted to MNRAS, 10 pages, 6 figure

A Phenomenological Thermodynamic Potential for CaTiO3 Single Crystal

The antiferrodistortive (AFD) structural transitions of calcium titanate (CaTiO3) at ambient pressure have been extensively studied during the last few years. It is found none of the AFD polymorphs is polar or ferroelectric. However, it was recently shown theoretically and later experimentally confirmed that a ferroelectric transition in CaTiO3 can be induced by tensile strains. The ferroelectric instability is believed to be strongly coupled to the AFD soft modes. In this article, we present a complete thermodynamic potential for describing the coupling between the AFD and ferroelectric phase transitions. We analyzed the dependence of transition temperatures on stress and strain condition. Based on this potential, a (001) CaTiO3 thin film diagram was constructed. The results show good agreement with available experimental observations. The strong suppression of ferroelectric transition by the AFD transition is discussed

Light-Induced Transitions of Polar State and Domain Morphology of Photo-Ferroelectric Nanoparticles

Using the Landau-Ginzburg-Devonshire approach, we study light-induced phase transitions, evolution of polar state and domain morphology in photo-ferroelectric nanoparticles (NPs). Light exposure increases the free carrier density near the NP surface and may in turn induce phase transitions from the nonpolar paraelectric to the polar ferroelectric phase. Using the uniaxial photo-ferroelectric Sn2P2S6 as an example, we show that visible light exposure induces the appearance and vanishing of striped, labyrinthine or curled domains and changes in the polarization switching hysteresis loop shape from paraelectric curves to double, pinched and single loops, as well as the shifting in the position of the tricritical point. Furthermore, we demonstrate that an ensemble of non-interacting photo-ferroelectric NPs may exhibit superparaelectric-like features at the tricritical point, such as strongly frequency-dependent giant piezoelectric and dielectric responses, which can potentially be exploited for piezoelectric applications.Comment: 42 pages, 7 figures, including 14 pages Supplement with 6 figure

Detection of the relativistic Shapiro delay in a highly inclined millisecond pulsar binary PSR J1012−-4235

PSR J1012$-$4235 is a 3.1ms pulsar in a wide binary (37.9 days) with a white dwarf companion. We detect, for the first time, a strong relativistic Shapiro delay signature in PSR J1012$-$4235. Our detection is the result of a timing analysis of data spanning 13 years and collected with the Green Bank, Parkes, and MeerKAT Radio Telescopes and the Fermi $\gamma$-ray space telescope. We measured the orthometric parameters for Shapiro delay and obtained a 22$\sigma$ detection of the $h_{\rm 3}$ parameter of 1.222(54) $\mu$s and a 200$\sigma$ detection of $\varsigma$ of 0.9646(49). With the assumption of general relativity, these measurements constrain the pulsar mass ($M_{\rm p}=1.44^{+0.13}_{-0.12}$M$_{\odot}$), the mass of the white dwarf companion ($M_{\rm c} = 0.270^{+0.016}_{-0.015}$M$_{\odot}$ ), and the orbital inclination ($i=88.06^{+0.28}_{-0.25} \deg$). Including the early $\gamma$-ray data in our timing analysis facilitated a precise measurement of the proper motion of the system of 6.58(5) mas yr$^{-1}$. We also show that the system has unusually small kinematic corrections to the measurement of the orbital period derivative, and therefore has the potential to yield stringent constraints on the variation of the gravitational constant in the future.Comment: Accepted for publication in Astronomy & Astrophysics, 10 pages, 8 figures, 3 table

The first interferometric detections of Fast Radio Bursts

We present the first interferometric detections of Fast Radio Bursts (FRBs), an enigmatic new class of astrophysical transient. In a 180-day survey of the Southern sky we discovered 3 FRBs at 843 MHz with the UTMOST array, as part of commissioning science during a major ongoing upgrade. The wide field of view of UTMOST ($\approx 9$ deg$^{2}$) is well suited to FRB searches. The primary beam is covered by 352 partially overlapping fan-beams, each of which is searched for FRBs in real time with pulse widths in the range 0.655 to 42 ms, and dispersion measures $\leq$2000 pc cm$^{-3}$. Detections of FRBs with the UTMOST array places a lower limit on their distances of $\approx 10^4$ km (limit of the telescope near-field) supporting the case for an astronomical origin. Repeating FRBs at UTMOST or an FRB detected simultaneously with the Parkes radio telescope and UTMOST, would allow a few arcsec localisation, thereby providing an excellent means of identifying FRB host galaxies, if present. Up to 100 hours of follow-up for each FRB has been carried out with the UTMOST, with no repeating bursts seen. From the detected position, we present 3$\sigma$ error ellipses of 15 arcsec x 8.4 deg on the sky for the point of origin for the FRBs. We estimate an all-sky FRB rate at 843 MHz above a fluence $\cal F_\mathrm{lim}$ of 11 Jy ms of $\sim 78$ events sky$^{-1}$ d$^{-1}$ at the 95 percent confidence level. The measured rate of FRBs at 843 MHz is of order two times higher than we had expected, scaling from the FRB rate at the Parkes radio telescope, assuming that FRBs have a flat spectral index and a uniform distribution in Euclidean space. We examine how this can be explained by FRBs having a steeper spectral index and/or a flatter log$N$-log$\mathcal{F}$ distribution than expected for a Euclidean Universe.Comment: 13 pages, 8 figures, 2 table

The UTMOST pulsar timing programme I: overview and first results

We present an overview and the first results from a large-scale pulsar timing programme that is part of the UTMOST project at the refurbished Molonglo Observatory Synthesis Radio Telescope (MOST) near Canberra, Australia. We currently observe more than 400 mainly bright southern radio pulsars with up to daily cadences. For 205 (8 in binaries, 4 millisecond pulsars) we publish updated timing models, together with their flux densities, flux density variability, and pulse widths at 843 MHz, derived from observations spanning between 1.4 and 3 yr. In comparison with the ATNF pulsar catalogue, we improve the precision of the rotational and astrometric parameters for 123 pulsars, for 47 by at least an order of magnitude. The time spans between our measurements and those in the literature are up to 48 yr, which allows us to investigate their long-term spin-down history and to estimate proper motions for 60 pulsars, of which 24 are newly determined and most are major improvements. The results are consistent with interferometric measurements from the literature. A model with two Gaussian components centred at 139 and $463~\text{km} \: \text{s}^{-1}$ fits the transverse velocity distribution best. The pulse duty cycle distributions at 50 and 10 per cent maximum are best described by log-normal distributions with medians of 2.3 and 4.4 per cent, respectively. We discuss two pulsars that exhibit spin-down rate changes and drifting subpulses. Finally, we describe the autonomous observing system and the dynamic scheduler that has increased the observing efficiency by a factor of 2-3 in comparison with static scheduling.Comment: 31 pages, 14 figures, 6 tables, accepted for publication in MNRA

The Application of Auxetic Material for Protective Sports Apparel

Current research of auxetic materials highlights its potential as personal protective equipment for sports apparel with enhanced properties such as conformability, superior energy absorption and reduced thickness. In contrast, commercially available protective materials have proven to be problematic in that they inhibit movement, breathability, wicking and that molded pads are prone to saddling. Foam components are embedded within personal protective equipment for sports apparel, where protective material is positioned at regions of the body frequently exposed to injury of the soft tissue through collision, falls or hard impact. At present, the impact resistance of auxetic open cell polyurethane foam and some additively manufactured auxetic structures have been established, and processes for manufacturing curved auxetic materials as well as molding methods have been developed. Despite this, auxetic materials have not yet been applied as personal protective equipment for sports apparel in current research. This paper argues that there is scope to investigate auxetic materials potential for enhanced wearer functionality through properties of synclastic curvature and biaxial expansion

A survey of localization in wireless sensor network

Localization is one of the key techniques in wireless sensor network. The location estimation methods can be classified into target/source localization and node self-localization. In target localization, we mainly introduce the energy-based method. Then we investigate the node self-localization methods. Since the widespread adoption of the wireless sensor network, the localization methods are different in various applications. And there are several challenges in some special scenarios. In this paper, we present a comprehensive survey of these challenges: localization in non-line-of-sight, node selection criteria for localization in energy-constrained network, scheduling the sensor node to optimize the tradeoff between localization performance and energy consumption, cooperative node localization, and localization algorithm in heterogeneous network. Finally, we introduce the evaluation criteria for localization in wireless sensor network