DEM simulation of cyclic tests on an offshore screw pile for floating wind

Screw piles need to be upscaled for offshore use e.g. being an alternative foundation and anchor form for offshore floating wind turbines, although the high demand of vertical installation forces could prevent its application if conventional pitch-matched installation is used. Recent studies, using numerical and centrifuge physical tests, indicated that the vertical installation force can be reduced by adopting over-flighting which also improved axial uplift capacity of the screw pile. The current study extends the scope to axial cyclic performance with respect to the installation approach. Using quasi-static discrete element method (DEM) simulation it was found that the over-flighted screw pile showed a lower displacement accumulation rate, compared to a pitch-matched installed pile, in terms of load-controlled cyclic tests. Sensitivity analysis of the setup of the cyclic loading servo shows the maximum velocity during the tests should be limited to avoid significant exaggeration of the pile displacement accumulation but this may lead to very high run durations.

Degradation performance and mechanism toward methyl orange via nanoporous copper powders fabricated by dealloying of ZrCuNiAl metallic glassy precursors

The catalyst of nanoporous Cu (NP-Cu) powders, with the chemical composition of Cu79.63Ni6.85O13.53 (at.%), was successfully fabricated by dealloying of Zr-Cu-Ni-Al metallic glassy precursors. The as-prepared NP-Cu powders, co-existing with Cu2O phase on Cu ligament surface, had a three-dimensional (3D) network porous structure. The NP-Cu powders/H2O2 system showed superior catalytic degradation efficiency toward azo dyes in both acidic (pH 2) and neutral (pH 7) environments. Moreover, the cyclic tests indicated that this powder catalyst also exhibited good durability. A novel degradation mechanism of NP-Cu powders/H2O2 was proposed: the high degradation performance in acidic environment was mainly derived from heterogeneous reaction involved with a specific pathway related to Cu3+ to produce HO•, while in neutral environment it was primarily resulted from homogeneous reaction with the generation of HO• from the classical Cu-based Fenton-like process. This work indicates that the NP-Cu powders have great potential applications as catalysts for wastewater treatments.

FEATURES OF MECHANICAL TESTS OF OSTEOSYNTHESIS SYSTEMS

Various methods of measuring the characteristics of stiffness and strength of systems "bone with a fracture - a means of fixation" are considered. Methods for measuring deformations of osteosynthesis systems are systematized, which take into account the nature of the action of external loads and allow to compare different systems of osteosynthesis. The rational arrangement of drugs at tests taking into account features of a structure of bones and the real loadings arising at functioning of musculoskeletal system is recommended. It is proposed to use the stiffness characteristics of the systems "bone - means of fixation" under the action of axial compression, transverse bending and torsion, including in cyclic modes; considered systems of osteosynthesis with the most common methods of fixing fractures to select the optimal in terms of quality methods of fixing fragments in fractures. It is established that the stability indicators of osteosynthesis systems, measured in the process of cyclic tests, are more sensitive to the type of fixing means and can be used to rank these systems according to the degree of mechanical reliability. The results of research obtained using these methods are implemented in surgical practice in the selection of optimal designs of fixation devices and the rational location of fixing elements.