A simplified fluid structure interaction model for the assessment of ship hard grounding

The structural damage of ships in navigational accidents is influenced by the hydrodynamic properties of surrounding water. Fluid structure interactions (FSI) in way of grounding contact can be idealized by combining commercial FEA tools and specialized hydrodynamic solvers. Despite the efficacy of these simulations, the source codes idealizing FSI are not openly available, computationally expensive and subject to limitations in terms of physical assumptions. This paper presents a unified FSI model for the assessment of ship crashworthiness following ship hard grounding. The method uses spring elements for the idealization of hydrostatic restoring forces in 3 DoF (heave, pitch, roll) and distributes the added masses in 6 DoF on the nodal points in way of contact. Comparison of results against the method of Kim et al. (2021) for the case of a barge and a Ro–Ro passenger ship demonstrate excellent idealization of ship dynamics. It is concluded that the method could be useful for rapid assessment of ship grounding scenarios and associated regulatory developments.

What’s new for the clinician? - Excerpts from and summaries of recently published papers

Endodontic files are used to remove intracanal pulpal tissues, microbial biofilm, and toxic by-products and to develop a continuously tapering canal while maintaining the canal geometry that ultimately allows for the delivery of irrigating solutions and intracanal medicaments as well as the three-dimensional filling of the root canal system. Historically, stainless steel hand files have been used to perform canal shaping. However, these files are stiff and associated with increased operator fatigue, and when used in the preparation of curved root canals, the restoring forces of the files tend to return the file back to its original shape, resulting in canal transportation.

The Association between the Extent of Late Gadolinium Enhancement and Diastolic Dysfunction in Hypertrophic Cardiomyopathy

Background Diastolic dysfunction in hypertrophic cardiomyopathy (HCM) patients is a frequent, yet poorly understood phenomenon. Purpose The purpose of this study is to assess the relationship between the myocardial fibrosis and diastolic dysfunction in patients with HCM. Materials and Methods We retrospectively investigated the impact of the myocardial fibrosis, as assessed by the extent of late gadolinium enhancement (LGE-%) on cardiac magnetic resonance imaging (CMRI), on diastolic dysfunction in 110 patients with HCM. The diastolic dysfunction was evaluated by the left atrial (LA) volume index measured on CMRI and lateral septal E/E′ ratio calculated on echocardiography. Results : There was a moderate correlation between the LGE-% and LA volume (r = 0.59, p < 0.0001). The logistic regression model of LGE-%, mitral regurgitation, and total left ventricular mass that investigated the independent predictors of LA volume identified LGE-% as the only independent parameter associated with the LA volume index (β = 0.30, p = 0.003). No correlation was observed between the LGE-% and E/E′(r = 0.24, p = 0.009). Conclusions Myocardial fibrosis in HCM patients is associated with a chronic diastolic burden as represented by increased LA volume. However, the fibrosis does not influence the E/E′ ratio, which is a well-known parameter of ventricular relaxation, restoring forces, and filling pressure.

Study on the SUAM Double Magnet System for Polishing

Superconductive assisted machining (SUAM) is a novel machining method that eliminates tool interference via magnetic levitation tools. In our study, we developed a double magnet system (DMS) to increase the maximum power of the holding force and stabilize the magnetic rotation during polishing via the higher magnetic flux compared to a single magnet system (SMS). The maximum magnetic flux density of the DMS was approximately 100 mT higher than that of the SMS. In these cases, the entire holding force increases as the distance between the superconducting bulk and lower magnet decreases. The attractive forces are maximum around a displacement of 6 mm, although the repulsive and restoring forces increase spontaneously. The polishing performances of the DMS on the SUS304 and A1100P plates were evaluated using water-based diamond slurries, for equal levitation amounts. The amount removed by the DMS increased for the A1100P and SUS304 substrates compared to that by the SMS. In this case, we observe that the deviation of the polishing area on the DMS decreases compared to that of the SMS, reflecting a more stable rotation and movement due to the higher holding force.

Measurements of periodically perturbed dewetting force fields and their consequences on the symmetry of the resulting patterns

We studied the origin of breaking the symmetry for moving circular contact lines of dewetting polymer films suspended on a periodic array of pillars. There, dewetting force fields driving polymer flow were perturbed by elastic micro-pillars arranged in a regular square pattern. Elastic restoring forces of deformed pillars locally balance driving capillary forces and broke the circular symmetry of expanding dewetting holes. The observed envelope of the dewetting holes reflected the symmetry of the underlying pattern, even at sizes much larger than the characteristic period of the pillar array, demonstrating that periodic perturbations in a driving force field can establish a well-defined pattern of lower symmetry. For the presented system, we succeeded in squaring the circle.

Implications of Buckingham's Pi Theorem to the Study of Similitude in Discrete Structures: Introduction of the RFN, μN and the SN Dimensionless Numbers and the Concept of Structural Speed

Motivated by the need to evaluate the seismic response of large capacity gravity energy storage systems (potential energy batteries) such as the proposed frictional Multiblock Tower Structures (MTS) recently discussed by Andrade et al. [1], we apply Buckingham's Pi Theorem [2] to identify the most general forms of dimensionless numbers and dynamic similitude laws appropriate for scaling discontinuous multiblock structural systems involving general restoring forces resisting inertial loading. We begin by introducing the dimensionless “mu-number” (μN) appropriate for both gravitational and frictional restoring forces and then generalize by introducing the “arbitrary restoring force number” (RFN). RFN is subsequently employed to study similitude in various types of discontinuous or discrete systems featuring frictional, gravitational, cohesive, elastic and mixed restoring forces acting at the block interfaces. In the process, we explore the additional consequences of inter and intra-block elasticity on scaling. We also formulate a model describing the mechanism of structural signal transmission for the case of rigid MTS featuring inter-block restoring forces composed of elastic springs and interfacial friction, introducing the concept of “structural speed”. Finally, we validate our results by demonstrating that dynamic time-histories of field quantities and structural speeds between MTS models at various scales are governed by our proposed similitude laws, thus demonstrating the consistency of our approach.

Calculating propulsive and restoring electromagnetic forces between massive circular coils of rectangular cross section with inclined axes in air

In this paper we give the new formulas for calculating the propulsive and the restoring electromagnetic forces between the loops in air whose centers are in the different axes. These new formulas are used to calculate the propulsive and the restoring forces between two inclined massive coils of rectangular cross section whose centers are in the different axes. The filament method is used. Results obtained by the presented approach are in remarkably good agreement with already published data. Electromagnetic forces can be used for various applications, it is very versatile; there are a plethora of ways to utilize electromagnetic forces and energy, from small scale uses e.g., microchips to larger scale and lifesaving uses e.g., radiotherapy.

Nonlinear and Stability Analysis of a Ship with General Roll-Damping Using an Asymptotic Perturbation Method

In this work, the response of a ship rolling in regular beam waves is studied. The model is one degree of freedom model for nonlinear ship dynamics. The model consists of the terms containing inertia, damping, restoring forces, and external forces. The asymptotic perturbation method is used to study the primary resonance phenomena. The effects of various parameters are studied on the stability of steady states. It is shown that the variation of bifurcation parameters affects the bending of the bifurcation curve. The slope stability theorems are also presented.

EXPERIMENTAL RESPONSE OF A LOW-YIELDING, SELF CENTERING, ROCKING COLUMN BASE JOINT WITH FRICTION DAMPERS

The sliding hinge joint (SHJ) is a supplemental energy dissipation system for column bases or beam-to-column connections of steel Moment Resisting Frames (MRFs). It is based on the application of symmetric/asymmetric friction dampers to develop a dissipative mechanism alternative to the column/beam yielding. This typology was initially proposed in New Zealand and, more recently, is starting to be tested and applied also in Europe. While on the one hand this technology provides great benefits such as the damage avoidance, on the other hand, due to the high unloading stiffness of the dampers in tension or compression, its cyclic response is typically characterized by a limited self-centering capacity.To address this shortcoming, the objective of the work herein presented is to examine the possibility to add to these connections also a self-centering capacity proposing new layouts based on a combination of friction devices (providing energy dissipation capacity), pre-loaded threaded bars and disk springs (introducing in the joint restoring forces).In this paper, as a part of an ongoing wider experimental activity regarding the behavior of self-centering connections, the attention is focused on the problem of achieving the self-centering of the column bases of MRFs by studying a detail consisting in a column-splice equipped with friction dampers and threaded bars with Belleville disk springs, located above a traditional full-strength column base joint. The main benefits obtained with the proposed layout are that: (i) the self-centering capability is obtained with elements (threaded bars and Belleville springs) which have a size comparable to the overall size of the column-splice cover plates; (ii) all the re-centering elements are moved far from the concrete foundation avoiding any interaction with the footing. The work reports the main results of an experimental investigation and the analysis of a MRF equipped with the proposed column base joints.

Stiffness Enhancement of a Superconducting Magnetic Bearing Using Shaped YBCO Bulks

© 2002-2011 IEEE. High-speed superconducting motors and generators stand to benefit from superconductor magnetic levitation bearings if their stiffness characteristics can be improved. Here we investigate a novel thrust bearing geometry, comprising a conical frustum shaped permanent magnet and matching superconducting toroid and puck assembly, aimed at producing high stiffness coupled with high levitation force. To this end, we have constructed a bearing test rig enabling measurements of the levitation force and stiffness of the assembly of YBa_2Cu_3O_{7-\delta } melt-textured bulks and Nd_2Fe_{14}B permanent magnet at temperatures down to 47 K. The experimental results are supported by finite element modeling that is validated against the experiment, and used to quantify the advantages of this configuration over a conventional cylindrical magnet and HTS puck arrangement. For axial displacements, the assembly produces higher and more consistent stiffness together with stronger restoring forces. For lateral displacements, the assembly produces up to double the lateral force and up to four times the stiffness. Our study also shows that the force contribution to the assembly from the small inner puck is negligible and it can therefore be eliminated from the bearing design.