Extraction of New Applicable Dimensionless Relations in the Wedge Impact Problem Using WCSPH Method

Impact problem associated with water entry of a wedge has important applications in various aspects of naval architecture and ocean engineering. In the present study, the 2DOF (2 Degrees of Freedom) wedge impact problem into the water with various wedge deadrise angles and impact velocities is investigated using Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) method. Artificial viscosity and density correction are used to create stability and also to prevent the penetration of fluid particles into the solid boundary. Solving the impact problem is very time-consuming, therefore extracting new mathematical relations can be very useful to calculate some important and applicable parameters in a certain range of wedge angles and impact velocities. In the present research, some new dimensionless applicable relations using the Buckingham π theorem are extracted to investigate important parameters such as acceleration and slamming force in general cases of a wedge impact problem. Then, these mathematical relations are validated by the results obtained from the simulations.

Social Image of Nursing. An Integrative Review about a Yet Unknown Profession

Background: Nursing is a discipline on which stereotypes have persisted throughout its history, considering itself a feminine profession and subordinated to the medical figure, without its own field of competence. All this leads to an image of the Nursing Profession that moves away from reality, constituting a real, relevant and high-impact problem that prevents professional expansion, and that has a direct impact on social trust, the allocation of resources and quality of care, as well as wages and professional satisfaction. The aim of this review was to identify and publicize the published material on the social image of Nursing, providing updated information about the different approaches to the subject. Methods: An integrative review of the literature has been made from primary sources of information published from 2010 to 2020. For this, the databases CINAHL, Scopus, SciELO, Dialnet and Cuiden have been consulted. Results: In total, 17 articles have been included in the review, with qualitative, quantitative, and even bibliographic reviews performed in countries such as Spain, Egypt, Argentina, Iran, Venezuela, Turkey, United Kingdom, and Australia. The results of those papers mostly showed that society has misinformation about the functions performed by nursing professionals, which is based on myths and stereotypes. Conclusions: Nursing is a profoundly unknown and invisible profession, as society continues without recognizing its competence, autonomy and independence.

Behavioral brittleness: the case for strategic behavioral public policy

Despite widespread recognition that behavioral public policy (BPP) needs to move beyond nudging if the field is to achieve more significant impact, problem-solving approaches remain optimized to achieve tactical success and are evaluated by short-term metrics with the assumption of stable systems. As a result, current methodologies may contribute to the development of solutions that appear well formed but become ‘brittle’ in the face of more complex contexts if they fail to consider important contextual cues, broader system forces, and emergent conditions, which can take three distinct forms: contextual, systemic, and anticipatory brittleness. The Covid-19 pandemic and vaccination rollout present an opportunity to identify and correct interventional brittleness with a new methodological approach – strategic BPP (SBPP) – that can inform the creation of more resilient solutions by embracing more diverse forms of evidence and applied foresight, designing interventions within ecosystems, and iteratively developing solutions. To advance the case for adopting a SBPP and ‘roughly right’ modes of inquiry, we use the Covid-19 vaccination rollout to define a new methodological roadmap, while also acknowledging that taking a more strategic approach may challenge current BPP norms.

A Time-Discontinuous Galerkin Finite Element Method for the Solution of Impact Problem of Gas-Saturated Coal

Based on the general Biot theory of saturated porous media, a modified time-discontinuous Galerkin finite element method (MDGFEM) is presented to simulate the structural dynamics and wave propagation problems of gas-saturated coal subjected to impact loading. Numerical results of one dimension and two dimensions show that the present MDGFEM possesses better abilities and provides much more accurate solutions than the traditional Newmark method and previous DGFEM for the impact problem. It can effectively capture the discontinuities of the wave and filter out the effects of spurious numerical oscillation induced by high-frequency impulsive load. The results can provide a technological basis for the research of the prevention of coal and gas dynamic disasters under deep mining. And the method could be useful for the further numerical research of coal-rock-gas coupling problems and coal-gas-heat coupling problems subjected to impact loading.

Dynamic Crack Propagation and Its Interaction With Micro-Cracks in an Impact Problem

The dynamic fracture behavior of brittle materials that contain micro-level cracks should be examined when material subjected to impact loading. We investigated the effect of micro-cracks on the propagation of macro-cracks that initiate from notch tips in the Kalthoff–Winkler experiment, a classical impact problem. To define predefined micro-cracks in three-dimensional space, we proposed a two-dimensional micro-crack plane definition in the bond-based peridynamics (PD) that is a non-local form of classical continuum theory. Randomly distributed micro-cracks with different number densities in a constant area and number in expending area models were examined to monitor the toughening of the material. The velocities of macro-crack propagation and the time required for completing fractures were considered in several predefined micro-cracks cases. It has been observed that toughening mechanism is only initiated by exceeding a certain number of micro-cracks; therefore, there is a positive correlation between the density of predefined micro-cracks and macro-crack propagation rate and, also, toughening mechanism.

Mechanisms-Based Transitional Viscoplasticity

When metal is subjected to extreme strain rates, the conversation of energy to plastic power, the subsequent heat production and the growth of damages may lag behind the rate of loading. The imbalance alters deformation pathways and activates micro-dynamic excitations. The excitations immobilize dislocation, are responsible for the stress upturn and magnify plasticity-induced heating. The main conclusion of this study is that dynamic strengthening, plasticity-induced heating, grain size strengthening and the processes of microstructural relaxation are inseparable phenomena. Here, the phenomena are discussed in semi-independent sections, and then, are assembled into a unified constitutive model. The model is first tested under simple loading conditions and, later, is validated in a numerical analysis of the plate impact problem, where a copper flyer strikes a copper target with a velocity of 308 m/s. It should be stated that the simulations are performed with the use of the deformable discrete element method, which is designed for monitoring translations and rotations of deformable particles.