In order to improve the fatigue resistance of orthotropic steel decks (OSDs), the steel bridge deck was annealed to reduce the welding residual stress of key welds. This work at first presented a systematical review and discussion over the distribution pattern of welding residual stress in OSDs, in accordance with a conceptual analysis respecting the impact of residual stress on fatigue crack propagation. Then, the associated summarization and comparison were made on the common approaches to mitigate the welding residual stress in the worldwide. By referring to the manufacturing of pressure vessels, the authors suggested to reduce welding residual stress by introducing annealing treatment to OSDs. On this basis, the study focused on the rib-to-deck welded joints that demonstrates a relatively prominent fatigue issue. The residual stress measurements and fatigue tests were carried out using a total of sixteen full-scale specimens, i. e., nine annealed specimens and seven as-welded ones without any additional treatment. The test results showed a reduction in the residual stress of welded joint in OSDs by 80% after the annealing, and moreover, an enhancement in the fatigue strength by 23% . Obviously, the annealing can significantly reduce the residual stress of the weld joints and effectively improve the fatigue resistance of OSDs.

In contrast with most existing results concerning unmanned aerial vehicles (UAVs) wherein material points or only attitude/longitudinal dynamics are considered, this article proposes a distributed fixed-time fault-tolerant control methodology for networked fixed-wing UAVs whose dynamics are six-degree-of-freedom with twelf-state-variables subject to actuator faults and full-state constraints. More precisely, state transformations with the scaling function are devised to keep the involved velocity and attitude within their corresponding constraints. The fixed-time property is obtained in the sense of guaranteeing that the settling time is lower bounded by a positive constant, which is independent of initial states. The actuator faults as well as the network induced errors are handled via the bound estimation approach and well-defined smooth functions. By strict Lyapunov arguments, all closed-loop signals are proved to be semiglobally uniformly ultimately bounded, and the tracking errors of velocity and attitude converge to the residual sets around origin within a fixed time.

Records from natural archives show that the strength of the East Asian summer monsoon (EASM) strongly depends on the orbital configuration of the Earth. However, the dominant orbital cycles driving EASM have been found to be spatially different. Speleothem stable oxygen isotopic records from southern China, which are believed to reflect large-scale changes in the Asian monsoon system, are dominated by climatic precession cycles. Further north, on the Chinese Loess Plateau (CLP), loess-and-paleosol sequences, which are argued to be controlled by monsoon intensity, are in pace with global ice volume changes dominated by obliquity, and after the mid-Pleistocene transition by 100-kyr cycles. To understand these critical discrepancies, here we apply a novel proxy based on the trace metal compositions of pedogenic carbonate in the eolian deposits on the CLP to reconstruct summer precipitation over the last 1.5 million years. Our reconstructions show that summer precipitation on the CLP is dominantly forced by obliquity not in pace with the ice-volume-imprinted loess-paleosol sequences before and after the mid-Pleistocene transition or with the precession-paced speleothem oxygen isotopic records. Coupled with climate model results, we suggest that the obliquity-driven variations of summer precipitation may originate from the gradient of boreal insolation that modulates the thermal contrast between the Asian continent and surrounding oceans.