Measured displacement fields constitute a rich database for the identification of mechanical behavior. A variety of methods are available today to address this problem. A formalism is proposed ...showing that they all revert to the minimization of a quadratic norm (or semi-norm) between measured and computed displacement fields. However, they differ in the chosen metric.
Transporting image noise through Digital Image Correlation and identification procedures, the uncertainty in the measured displacement fields (i.e., their full covariance) and the resulting uncertainty in the estimated constitutive parameters is assessed. Consequently, an optimal choice of metric (with respect to image noise) is proposed so that the resulting identification uncertainty is minimized.
Advances in friction stir spot welding Shen, Zhikang; Ding, Yuquan; Gerlich, Adrian P.
Critical reviews in solid state and materials sciences,
11/1/2020, 2020-11-01, 20201101, Volume:
45, Issue:
6
Journal Article
Peer reviewed
Friction stir spot welding (FSSW) is a variation of linear Friction Stir Welding (FSW), which was invented to compete with resistance spot welding (RSW) and riveting of lightweight alloys in the ...automobile, shipbuilding and aerospace industries. Recently, the application of FSSW has rapidly extended to a variety of metals and nonmetals. This article provides a comprehensive review of the recent progress on the process fundamentals, parameters optimization, microstructural evolution and mechanical properties, and relevant simulation and modeling of FSSW. The article also evaluates the energy generation, temperature distribution, plastic flow and joining mechanisms. The optimizations of tool design and welding parameters are obtained through experiments and modeling. Furthermore, a particular emphasis is given to microstructural characterization of the recovery, recrystallization and grain growth, and related annealing phenomena after in the welded alloys. The mechanisms of defect formation and liquidation cracking are discussed in detail. The mechanical properties, including hardness, static strength, fatigue performance and failure mechanisms and the relationship between mechanical properties and microstructures are also addressed along with residual stress and corrosion behavior.
Selective laser melting (SLM) additive manufacturing of pure tungsten encounters nearly all intractable difficulties of SLM metals fields due to its intrinsic properties. The key factors, including ...powder characteristics, layer thickness, and laser parameters of SLM high density tungsten are elucidated and discussed in detail. The main parameters were designed from theoretical calculations prior to the SLM process and experimentally optimized. Pure tungsten products with a density of 19.01 g/cm
3
(98.50% theoretical density) were produced using SLM with the optimized processing parameters. A high density microstructure is formed without significant balling or macrocracks. The formation mechanisms for pores and the densification behaviors are systematically elucidated. Electron backscattered diffraction analysis confirms that the columnar grains stretch across several layers and parallel to the maximum temperature gradient, which can ensure good bonding between the layers. The mechanical properties of the SLM-produced tungsten are comparable to that produced by the conventional fabrication methods, with hardness values exceeding 460 HV
0.05
and an ultimate compressive strength of about 1 GPa. This finding offers new potential applications of refractory metals in additive manufacturing.
The conventional parameter identification process generally assumes that parameters remain constant. However, under extreme loading conditions, structures may exhibit nonlinear behavior, and ...parameters could demonstrate time‐variant characteristics. The unscented Kalman filter (UKF), as an efficient online recursive estimator, is widely used for identifying parameters of nonlinear systems. Nevertheless, it exhibits limitations when attempting to identify time‐variant parameters. To address this issue, this paper proposes a covariance matching technique that produces an array of adaptive UKF algorithms. Firstly, the sensitivity parameter η is defined to identify the instant when the parameter change occurs, and its threshold is calculated based on the sensitivity parameter time history curve. Secondly, an adaptive forgetting factor is introduced to simultaneously update the innovation, cross, and state covariance matrices when the kth‐step sensitive parameter surpasses the threshold. Finally, a secondary correction forgetting factor (SCFF) is employed to further re‐update the state covariance values at the identified damage locations. This creative step enhances the adaptive capability and optimizes the identification accuracy of the proposed algorithms. Both the numerical simulations and shaking table test demonstrate that the proposed adaptive algorithms can efficiently identify the time‐variant stiffness‐type parameters, and accurately capture their time‐variant characteristics.
In this brief communication we provide the rationale for and the outcome of the International Astronomical Union (IAU) resolution vote at the XXIXth General Assembly in Honolulu, Hawaii, in 2015, on ...recommended nominal conversion constants for selected solar and planetary properties. The problem addressed by the resolution is a lack of established conversion constants between solar and planetary values and SI units: a missing standard has caused a proliferation of solar values (e.g., solar radius, solar irradiance, solar luminosity, solar effective temperature, and solar mass parameter) in the literature, with cited solar values typically based on best estimates at the time of paper writing. As precision of observations increases, a set of consistent values becomes increasingly important. To address this, an IAU Working Group on Nominal Units for Stellar and Planetary Astronomy formed in 2011, uniting experts from the solar, stellar, planetary, exoplanetary, and fundamental astronomy, as well as from general standards fields to converge on optimal values for nominal conversion constants. The effort resulted in the IAU 2015 Resolution B3, passed at the IAU General Assembly by a large majority. The resolution recommends the use of nominal solar and planetary values, which are by definition exact and are expressed in SI units. These nominal values should be understood as conversion factors only, not as the true solar/planetary properties or current best estimates. Authors and journal editors are urged to join in using the standard values set forth by this resolution in future work and publications to help minimize further confusion.
In this investigation the attention is given to a mathematical model of the Newtonian liquid over an unsteady stretching sheet under the combined effects of different natural parameters with heat and ...mass transfer. The movement of a laminar thin liquid film and associated heat and mass transfer from a horizontal stretching surface is studied. Magnetic field is imposed perpendicular to the direction of flow while, surface tension is varied quadratically with temperature of the conducting fluid for viscous incompressible free surface flow. Furthermore, mixed convection, variation of thermal conductivity and viscosity (linear function of temperature) of the flow are examined. Moreover, effects of source/sink on mass and heat transfer of an unsteady thin film flow with pressure are also investigated. The transformation allows to convert the boundary layer model to a system of nonlinear ODEs (ordinary differential equations). Analytical and Numerical solutions of the resulting nonlinear ODEs are obtained by using HAM and BVP4C package. Thickness of the boundary layer is investigated by both methods, for a classical selection of the unsteadiness parameter. Present observation displays, the joined effects of source/sink (on mass and heat transfer), mixed convection and magnetic field is to improve the thermal boundary layer thickness. Results for the Sherwood number, heat flux (Nusselt number), skin friction coefficient and free surface temperature are granted graphically and in a table form. The flow is accountable to a chemical reaction, heat source and radiation absorption effects are pretended to be meaningful while taking into account the effect of Hartman number. Similarly, the effects of natural parameters such as thermocapillary number, Prandtl number and Schmidt number on the velocity, temperature and solute concentration are investigated.
•Observations of mixed convection, source/sink, radiation/absorption and chemical reaction.•Variation of viscosity and thermal conductivity on an unsteady stretching sheet along pressure effect, with magnetic field.•Surface tension quadratically varies with temperature.•Homotopy Analysis Method (HAM) and numerical BVP4C are used for solution purpose.•Effects of heat and mass transfer.
We uncover a local order parameter for measurement-induced phase transitions: the average entropy of a single reference qubit initially entangled with the system. Using this order parameter, we ...identify scalable probes of measurement-induced criticality that are immediately applicable to advanced quantum computing platforms. We test our proposal on a 1 + 1 dimensional stabilizer circuit model that can be classically simulated in polynomial time. We introduce the concept of a "decoding light cone" to establish the local and efficiently measurable nature of this probe. We also estimate bulk and surface critical exponents for the transition. Developing scalable probes of measurement-induced criticality in more general models may be a useful application of noisy intermediate scale quantum devices, as well as point to more efficient realizations of fault-tolerant quantum computation.
99.9%. The undertaken analysis has confirmed the earlier obtained conclusion on the possibility to extract the main aeronomic parameters from the routine ionosonde observations with the THERION ...method.
ABSTRACT
In Galaxy And Mass Assembly Data Release 4 (GAMA DR4), we make available our full spectroscopic redshift sample. This includes 248 682 galaxy spectra, and, in combination with earlier ...surveys, results in 330 542 redshifts across five sky regions covering ∼250 deg2. The redshift density, is the highest available over such a sustained area, has exceptionally high completeness (95 per cent to rKiDS = 19.65 mag), and is well-suited for the study of galaxy mergers, galaxy groups, and the low redshift (z < 0.25) galaxy population. DR4 includes 32 value-added tables or Data Management Units (DMUs) that provide a number of measured and derived data products including GALEX, ESO KiDS, ESO VIKING, WISE, and HerschelSpace Observatory imaging. Within this release, we provide visual morphologies for 15 330 galaxies to z < 0.08, photometric redshift estimates for all 18 million objects to rKiDS ∼ 25 mag, and stellar velocity dispersions for 111 830 galaxies. We conclude by deriving the total galaxy stellar mass function (GSMF) and its sub-division by morphological class (elliptical, compact-bulge and disc, diffuse-bulge and disc, and disc only). This extends our previous measurement of the total GSMF down to 106.75 M$_{\odot } \, h_{70}^{-2}$ and we find a total stellar mass density of ρ* = (2.97 ± 0.04) × 108 M$_{\odot } \, h_{70}$ Mpc−3 or $\Omega _*=(2.17 \pm 0.03) \times 10^{-3} \, h_{70}^{-1}$. We conclude that at z < 0.1, the Universe has converted 4.9 ± 0.1 per cent of the baryonic mass implied by big bang Nucleosynthesis into stars that are gravitationally bound within the galaxy population.
HPV-positive cancer is strongly immunogenic tumor which induces cell type response in surrounding microenvironment. Systemic inflammation is generally accompanied by cancer disease and it weakens ...cell response and negatively influences organism reaction to cancer
The aim of present study was to compare laboratory parameters of the immune system: leukocyte count (WBC), neutrophil count (Neut) and lymphocyte count (Lym), monocyte count (Mono), C-reactive protein (CRP), Interleukine 6 (Il-6), in patients with HPV-positive and HPV-negative OPC.
75 patients were treated with curative intent with radiotherapy alone (32 %) or combined with platinum-based chemotherapy (68%). There were 47% patients with T1/2 and 53% with T3/4 of primary tumor stage and 44% and 56% of patients with N0 and N+ nodal stage disease, respectively. Complete blood counts (CBC), C-reactive protein (CRP) and Il-6 were estimated in blood or serum before and after the treatment. HPV DNA was determined in plasma by QPCR method.
In patients with HPV-negative OPC WBC count (p=0,006 median: 6,88 vs 5,69), Lym count (p=0,02 median: 1,96 vs 1,49) and CRP (p=0,0001 median: 5,88 vs 1,35 mg/dl) was higher than for HPV-positive OPC before treatment. Additionally, in patients with HPV-negative OPC WBC count (p=0,03 median: 5,53 vs 4,17), Lym count (p=0,02 median: 0,69 vs 0,44), Mono count (p=0,003 median: 0,58 vs 0,43) and Il-6 (p=0,05 median: 25,53 vs 11,65 pg/ml) was higher than for HPV-positive OPC after therapy. Before treatment significantly longer overall survival (OS) for patients with low WBC count (p=0,001)(Fig.1), low concentration of CRP (p=0,0001) (Fig. 2) and Il-6 (p=0,01) was also found.
Inflammation processes are more severe in HPV-negative OPC. Low levels of inflammatory indicators like WBC count, Lym count, CRP, Il-6 may be associated with longer OS in this group of patients. Systemic inflammation reflects host reaction on cancer, characterized by a significant weakness of cellular immunity. It is more characteristic for patients with HPV–negative OPC
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