Ultralight vector dark matter search using data from the KAGRA O3GK run

Among the various candidates for dark matter (DM), ultralight vector DM can be probed by laser interferometric gravitational wave detectors through the measurement of oscillating length changes in the arm cavities. In this context, KAGRA has a unique feature due to differing compositions of its mirrors, enhancing the signal of vector DM in the length change in the auxiliary channels. Here we present the result of a search for U(1)B−L gauge boson DM using the KAGRA data from auxiliary length channels during the first joint observation run together with GEO600. By applying our search pipeline, which takes into account the stochastic nature of ultralight DM, upper bounds on the coupling strength between the U(1)B−L gauge boson and ordinary matter are obtained for a range of DM masses. While our constraints are less stringent than those derived from previous experiments, this study demonstrates the applicability of our method to the lower-mass vector DM search, which is made difficult in this measurement by the short observation time compared to the auto-correlation time scale of DM

STRENGTHENING MECHANISMS IN Nb-Ti-V MICROALLOYED STEEL

Yield strength of Nb-Ti-V microalloyed steel has been investigated as a function of its microstructure obtained after industrial rolling on a hot strip mill. Optical (OM) and transmission electron microscopy (TEM) were used to reveal the ferrite grain structure, fine carbonitride precipitation and dislocation substructures. It was found that the effects of solid solution and grain size hardening were not sufficient to justify the results of tensile testing. Additional strengthening was attributed to carbonitride precipitation in austenite, interphase precipitation during transformation, and the formation of dislocations. All contributions of these microstructural features on mechanical property were estimated from empirical models available from literature. A global effect of both austenite and interphase carbonitride precipitation hardening was proposed. It was verified that yield strength calculated from cumulative effect of different strengthening mechanisms has presented good fitting with experimental tensile test

Grãos ultrafinos por laminação a morno e recozimento intercrítico

Grain refinement of low carbon steel via the warm deformation of martensite during torsion testing was investigated. At the beginning of straining, laths with high dislocation density were observed. After large deformations, a ferrite matrix with grain size close to 1μm and dispersed cementite particles were attained