Numerical study on the effect of welding and heating treatments on strength of high strength steel column

[EN] High strength steel box columns are usually fabricated from steel slab by applying welding. The welding process can introduce residual stresses and geometric imperfections into the columns and influence the column strength. In this study, a numerical investigation on the behavior of high strength steel thin-walled box columns under the compression force was carried out. The welding processes were firstly simulated with commercial package ABAQUS in this study to find out the residual stress distributions in high strength steel box column. After that, the column behaviors under the compression were modelled with predefined field from the previous step. The effect of the welding process (including flux-core arc welding and submerged arc welding), heating treatment (including preheating and post-weld heat treatment) and geometrical imperfection on the residual stress field and box column strength was investigated and discussed.Jin, J.; Bao, W.; Liu, J.; Peng, Z. (2018). Numerical study on the effect of welding and heating treatments on strength of high strength steel column. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 667-673. https://doi.org/10.4995/ASCCS2018.2018.8370OCS66767

Direct neutron capture cross sections of 62Ni in the s-process energy range

Direct neutron capture on 62Ni is calculated in the DWBA and the cross sections in the energy range relevant for s-process nucleosynthesis are given. It is confirmed that the thermal value of the capture cross section contains a subthreshold resonance contribution. Contrary to previous investigations it is found that the capture at higher energies is dominated by p-waves, thus leading to a considerably increased cross section at s-process energies and a modified energy dependence.Comment: 10 pages, 1 figure, corrected typos in Eq. 6 and subsequent paragrap

SU(2)-in-SU(1,1) Nested Interferometer for Highly Sensitive, Loss-Tolerant Quantum Metrology

We present experimental and theoretical results on a new interferometer topology that nests a SU(2) interferometer, e.g., a Mach-Zehnder or Michelson interferometer, inside a SU(1,1) interferometer, i.e., a Mach-Zehnder interferometer with parametric amplifiers in place of beam splitters. This SU(2)-in-SU(1,1) nested interferometer (SISNI) simultaneously achieves high signal-to-noise ratio (SNR), sensitivity beyond the standard quantum limit (SQL) and tolerance to photon losses external to the interferometer, e.g., in detectors. We implement a SISNI using parametric amplification by four-wave mixing (FWM) in Rb vapor and a laser-fed Mach-Zehnder SU(2) interferometer. We observe path-length sensitivity with SNR 2.2 dB beyond the SQL at power levels (and thus SNR) 2 orders of magnitude beyond those of previous loss-tolerant interferometers. We find experimentally the optimal FWM gains and find agreement with a minimal quantum noise model for the FWM process. The results suggest ways to boost the in-practice sensitivity of high-power interferometers, e.g., gravitational wave interferometers, and may enable high-sensitivity, quantum-enhanced interferometry at wavelengths for which efficient detectors are not available.Comment: 6 pages + 4 of supplemental material, 5 figure

Effects of Spartina alterniflora invasion on distribution of Moerella iridescens in a tidal flat of western Pacific Ocean

The invasion of Spartina alterniflora significantly affected the local ecosystem of Western Pacific Ocean where Moerella iridescens lives. Five patches with different invasion stages of S. alterniflora were selected and the influence on distribution of M. iridescens was studied on the coast of Wenzhou Bay, China in 2007. The aggregated distribution pattern was proved by using Taylor's power regression and Iwao's plot regression methods (p<0.001). The densities were significantly affected by the factors of S. alterniflora invasion stage and season (p<0.001), but no significant effect of interaction (p=0.805) occurred. M. iridescens mainly clumped in the habitats of no invasion and initial invasion of S. alterniflora was in the high tidal zone, and the lowest density was recorded where complete invasion occurred. The densities were larger in warmer than in cooler seasons. There were significant positive correlations among the average densities in seasons. Density variation must be the response of M. iridescens to the environment, including S. alterniflora invasion stage, temperate stress and interspecific associations

Spectral hardness evolution characteristics of tracking Gamma-ray Burst pulses

Employing a sample presented by Kaneko et al. (2006) and Kocevski et al. (2003), we select 42 individual tracking pulses (here we defined tracking as the cases in which the hardness follows the same pattern as the flux or count rate time profile) within 36 Gamma-ray Bursts (GRBs) containing 527 time-resolved spectra and investigate the spectral hardness, $E_{peak}$ (where $E_{peak}$ is the maximum of the $\nu F_{\nu}$ spectrum), evolutionary characteristics. The evolution of these pulses follow soft-to-hard-to-soft (the phase of soft-to-hard and hard-to-soft are denoted by rise phase and decay phase, respectively) with time. It is found that the overall characteristics of $E_{peak}$ of our selected sample are: 1) the $E_{peak}$ evolution in the rise phase always start on the high state (the values of $E_{peak}$ are always higher than 50 keV); 2) the spectra of rise phase clearly start at higher energy (the median of $E_{peak}$ are about 300 keV), whereas the spectra of decay phase end at much lower energy (the median of $E_{peak}$ are about 200 keV); 3) the spectra of rise phase are harder than that of the decay phase and the duration of rise phase are much shorter than that of decay phase as well. In other words, for a complete pulse the initial $E_{peak}$ is higher than the final $E_{peak}$ and the duration of initial phase (rise phase) are much shorter than the final phase (decay phase). This results are in good agreement with the predictions of Lu et al. (2007) and current popular view on the production of GRBs. We argue that the spectral evolution of tracking pulses may be relate to both of kinematic and dynamic process even if we currently can not provide further evidences to distinguish which one is dominant. Moreover, our statistical results give some witnesses to constrain the current GRB model.Comment: 32 pages, 26 figures, 3 tables, accepted for publication in New Astronom

Stability of the doped antiferromagnetic state of the t-t'-Hubbard model

The next-nearest-neighbour hopping term t' is shown to stabilize the AF state of the doped Hubbard model with respect to transverse perturbations in the order- parameter by strongly suppressing the intraband particle-hole processes. For a fixed sign of t', this stabilization is found to be significantly different for electron and hole doping, which qualitatively explains the observed difference in the degree of robustness of the AF state in the electron-doped (Nd_{2-x}Ce_{x}CuO_{4}) and hole-doped (La_{2-x}Sr_{x}CuO_{4}) cuprates. The t'-U phase diagram is obtained for both signs of the t' term, showing the different regions of stability and instability of the doped antiferromagnet. Doping is shown to suppress the t'-induced frustration due to the competing interaction J'. A study of transverse spin fluctuations in the metallic AF state reveals that the decay of magnons into particle-hole excitations yields an interesting low-energy result \Gamma \sim \omega for magnon damping.Comment: 10 pages, 8 figure

Asymmetric nuclear matter in a Hartree-Fock approach to non-linear QHD

The Equation of State (EOS) for asymmetric nuclear matter is discussed starting from a phenomenological hadronic field theory of Serot-Walecka type including exchange terms. In a model with self interactions of the scalar sigma-meson we show that the Fock terms naturally lead to isospin effects in the nuclear EOS. These effects are quite large and dominate over the contribution due to isovector mesons. We obtain a potential symmetry term of "stiff" type, i.e. increasing with baryon density and an interesting behaviour of neutron/proton effective masses of relevance for transport properties of asymmetric dense matter.Comment: 12 pages (LATEX), 3 Postscript figures, revised versio