Rocking Motion Research Articles

Effect of Rocking Motion Created Using Multiple Linear Actuators on Deformation Behavior in Upsetting Process

Forging load generally increases for many reasons as compression proceeds. To reduce the forging load, we focused on reducing the contact area with forging dies and proposed a new method using the flexible rocking motion created in coordination with multiple linear actuators. A cylindrical specimen of annealed pure aluminum was upset between flat dies up to half its initial height. Rocking motion was applied to the lower die in the latter half of the compression. The presented method reduced the forging load by up to approximately 50% compared with conventional upsetting. The reduction of load increased with increasing rocking angle and its frequency. The upset specimen was spread more toward the rocking direction and its end face processed with the rocking die was slightly tapered. Lubrication caused sliding of the specimen during rocking even with a small rocking angle.

Resilience of museum contents

The relationship between exhibitions and museum audiences has strongly changed in recent years. In an ongoing attempt to engage people and maintain audiences, new museums as well as those under renovation have acknowledged the importance of offering creative spaces. The pendulum has swung from the museum as a temple to keep treasures to the museum as an active space, a toolbox. Today’s audiences are no longer looking for a cold ‘white cube’ museum experience. Instead, they are looking for warmer, shared experiences, i.e. people can be closer to the artefact and even touch it. This has induced attempts to exhibit museum artefacts in different ways. Nevertheless the exhibition devices for museums ought to be designed or strengthened to comply with the need of safety not only for the artefact but also for the visitors, in the sense established by current codes and regulations. Unfortunately the actions to which the artefacts are actually subjected are of different types. In addition to those related to the climate and environment changes, there are those due to the actions typical of the museum site, like the earthquakes, and those related to the political and cultural changes. The roots of the problem dates back to the first years of the sixties and only recently has been applied to the museum contents. An artefact can be in fact considered a rigid object placed on a shaking base that may enter a rocking motion and result in overturning.

Excited state proton transfer processes of pyranine studied by femtosecond stimulated Raman spectroscopy

As one of the most fundamental processes, proton transfer reaction plays an important role in chemical and biological process, and to reveal the choreography of the proton motion intra- and intermolecularly, a spectroscopic technique capable of capturing molecular structural dynamics of excited-state proton transfer motions on an intrinsic time scale is needed. In this study, We utilize wavelength-tunable femtosecond stimulated Raman spectroscopy with a time resolution of ~100 fs, spectral resolution of 15 cm<sup>–1</sup> and spectral range of 400 cm<sup>–1</sup>—1800 cm<sup>–1</sup>, combined with traditional transient absorption spectroscopywith a time window between 0 and 600 ps to simultaneously achieve reaction dynamics for transient reactant and product of the photoacid pyranine (8-hydroxypyrene1, 3, 6-trisulfonic acid, HPTS) molecules undergoing excited-state proton transfer reaction in complex with water and acetate molecules. Marker bands attributed to the deprotonated form of HPTS in a frequency range from 400 cm<sup>–1</sup> to 1700 cm<sup>–1</sup> are obtained under the excitation of 400 nm laser pulses. The marker band at 1516 cm<sup>–1</sup>, which is assigned to phenolic ring carbon carbon double band stretching accompanied with carbon hydrogen in-plane rocking motions, exhibits complex rise and decay dynamics. The simultaneously observed excited-state Raman mode at 920 cm<sup>–1</sup> which is assigned to the excited carbon-carbon single bond stretch mode in the protonated acetic acid root molecule, helps us to clearly resolve the reaction rates of excited-state proton transfer. Based on the multi-exponential fitting results, the dynamics of excited-state Raman mode at 920 cm<sup>–1</sup> exhibits bi-exponential processes with time constants of ~470 fs and ~3 ps. The ultrafast time component indicates that the excited-state proton transfer originates from an HPTS-acetate complex, indicating that part of the ground-state HPTS molecules are in the “tight” hydrogen bonding configuration that can quickly shift the excited-state proton charge toward the acetate acceptor molecule through a direct hydrogen bond. The second slower time component implies a significant subpopulation of HPTS in the ground state, i.e. hydrogen bonds to an acetate ion via an intervening water molecule, and upon photo excitation, the proton transfers to the water solvent before proton is picked up by the acetate ion.

A study on the behavior of structures based on the rocking motion of rigid cores involving pre-compressed springs and viscous dampers

To create a partial rocking mode in a building structure during an earthquake, two or more rigid cores with joint connection to the foundation, and capable of moving in the two main directions of the building’s plan, can be used. A rigid core with a hinge connection to the foundation is essentially unstable. However, two rigid cores can be connected together by springs and dampers in certain floors to create a stable structure. At the same time, the structure shows a rocking behavior in which the building moves almost as a rigid body. In fact, the effects of all modes other than the fundamental one is almost eliminated. The use of yielding or friction dampers leads to permanent displacements in the structure in an earthquake. Therefore, in this study pre-compressed springs were employed, which do not create any permanent displacement. The pre-compressed springs were used to provide the structure with initial stiffness and prevent any displacement by small forces. Since an elastic spring does not have any damping, it was decided to control the structural displacements by viscous dampers in certain floors. Finally, the proposed structure underwent static and time-history analyses in plastic range, and the results suggested the desirable behavior of the proposed structure. In particular, there were no permanent displacements left in the structure after the earthquake.

A Simplified Model for Investigation on the Effects of Seismic Actions on Masonry Arch Bridges

Masonry bridges are vulnerable structural systems to the ground motion excitation and their survival in case of such incidents has to be studied in detail. In this work, a simplified model for dynamic analysis of masonry bridges based on rocking motion of rigid blocks is proposed. Using this model, nonlinear time integration analysis on these bridges can be done with ease and in a short time. The proposed model was used in evaluation of seismic performances of a monumental masonry bridge subjected to both horizontal and vertical seismic actions. The study shows the importance of vertical component of ground motion in determination of internal forces and shear sliding deformation at bottom of the bridge’s pier. The proposed model has also shown its ability in defining the effectiveness of a seismic retrofit approach for the same bridge system in a comparative study. According to this investigation, seismic performances of the bridge can be significantly improved in case of adding ductility to its deck assembly.

Improved pivot–slide model of the motion of a curling rock

The pivot–slide model (Shegelski and Lozowski) successfully predicts the slide and curl distances of a curling rock. However, in this model, there is no dependence of the curl distance on the initial velocity, because the ratio between the pivot to sliding times is constant. A refined model is presented, in which the ratio of the pivot to sliding times depends on the stone velocity via two parameters. Confidence limits for these parameters are deduced from experimental data, which show that the pivot–slide ratio depends on the stone velocity. However, precise values of these parameters could not be obtained with this study, as more precise experiment data are needed. The refined model allows one to qualitatively explain two characteristics of the stone trajectory observed in a curling game, namely the bigger final curl with lower initial velocity and the lower curl with the effect of sweeping the ice.

Viaduct seismic response under spatial variable ground motion considering site conditions

The evaluation of the seismic hazard for a given site is to estimate the seismic ground motion at the surface. This is the result of the combination of the action of the seismic source, which generates seismic waves, the propagation of these waves between the source and the site, and site local conditions. The aim of this work is to evaluate the sensitivity of dynamic response of extended structures to spatial variable ground motions (SVGM). All factors of spatial variability of ground motion are considered, especially local site effect. In this paper, a method is presented to simulate spatially varying earthquake ground motions. The scheme for generating spatially varying ground motions is established for spatial locations on the ground surface with varying site conditions. In this proposed method, two steps are necessary. Firstly, the base rock motions are assumed to have the same intensity and are modelled with a filtered Tajimi-Kanai power spectral density function. An empirical coherency loss model is used to define spatial variable seismic ground motions at the base rock. In the second step, power spectral density function of ground motion on surface is derived by considering site amplification effect based on the one dimensional seismic wave propagation theory. Several dynamics analysis of a curved viaduct to various cases of spatially varying seismic ground motions are performed. For comparison, responses to uniform ground motion, to spatial ground motions without considering local site effect, to spatial ground motions with considering coherency loss, phase delay and local site effects are also calculated. The results showed that the generated seismic signals are strongly conditioned by the local site effect. In the same sense, the dynamic response of the viaduct is very sensitive of the variation of local geological conditions of the site. The effect of neglecting local site effect in dynamic analysis gives rise to a significant underestimation of the seismic demand of the structure.

The initial high-energy phenomena of earthquake sources in fluid-saturated environments

Experimental data pertaining to weak faults requires construction of microscopic models of the earthquake sources. This study proposes a new high-energy mechanism of transformation of potential energy of strata, saturated with free or bounded fluids, into a kinetic energy of motion of rocks. The proposed approach relies within the framework of classic statistical theory. The high-energy phenomena at a nanometer level are generated by self-consistent molecular fields acting on individual particles. The analysis is carried out using the Bogolyubov-Born-Green-Kirkwood-Yvon equations for the particle group distribution functions. We have investigated the number of high-energy phenomena: (1) the emission of atoms and molecules with high energies from the abruptly opened surface of a condensed system; (2) the implosion of convergent streams of high-energy particles, accompanied by a phenomena of their shock dissociation and ionization, with a subsequent formation of partially ionized plasma; and (3) the recombination processes inside a plasma leading to a formation of molecules with high kinetic energies. The initiation of an earthquake occurs due to an abrupt opening of a cavity in the fluid-saturated medium. At certain thermodynamic conditions, the work function of atoms and molecules from the surface of the system may take negative values. As a result, the emission of molecules of fluids from the cavity walls will generate the high-speed streams of molecules. The emitted flux of molecules leads to the phenomena of implosion, impact dissociation, and ionization of the molecules. This plasma state of the medium is sufficient for an explosion. The explosion initiates a self-supporting chain of consequent explosions in a plane of the tectonic fault. As an example, we have considered the Bridgman explosion of serpentinite.

Reply to the Comment on “A Scratch-Guide Model for the Motion of a Curling rock”

Several issues were raised in the Comment on “A scratch-guide model for the motion of a curling rock”. A reply to these comments is provided.

Comment on “A Scratch-Guide Model for the Motion of a Curling Rock”

For several years, there has been disagreement in the literature over the “scratch-guiding mechanism” first published by Nyberg et al. (Wear 301:583–589, 2013) in 2013 and recently quantified by Penner (Tribol Lett 67:35.1–35.13, 2019) in 2019. According to this proposal, the lateral motion of curling rocks can be influenced by pre-existing scratches on the ice. In particular, it is argued that scratches made by the front of the running band can “push” the back of the running band to the left or to the right, depending on their orientation. We offer here a critique of the Penner paper (Penner in Tribol Lett 67:35.1–35.13, 2019), alluding inter alia to recently published experimental results (Shegelski and Lozowski https://doi.org/10.1177/1754337118821575, 2019), which clearly demonstrate that scratches made by the running band of a curling rock have no influence on the trajectories of a subsequent rock travelling over those scratches. We also point out some apparent inconsistencies and deficiencies in the Penner model itself.

Dysphagia in Progressive Supranuclear Palsy.

Progressive supranuclear palsy (PSP) is the most common Parkinson-Plus syndrome and is associated with early onset of dysphagia relative to Parkinson Disease. The current study contributes to the growing understanding of swallowing dysfunction in PSP by describing oropharyngeal swallowing characteristics in a large prospective cohort of participants with PSP employing a nationally standardized videofluoroscopy protocol and a disease severity scale developed expressly for PSP. Participants were 51 adults diagnosed with PSP. Each participant underwent a clinical interview and standardized videofluorographic assessment. Swallowing function was characterized with the Modified Barium Swallow Impairment Scale (MBSImP) and Penetration-Aspiration Scale (PAS). Variables of interest were participant-reported difficulties with liquids and/or solids; overall impression score for each of the 17 individual MBSImP components, as well as Oral Total Sum and Pharyngeal Total Sum; and PAS. Data were described with median interquartile range, counts, and proportions. Spearman's rank correlations were calculated between MBSImP scores and participant-reported indices, FOIS, and PSP Rating Scale. Approximately two-thirds of participants reported difficulties with liquids, solids, or both, although fewer than 15% reported modifying consistencies. Videofluorographic findings included predominant oral phase impairments, including back and forth rocking motion of the tongue, delayed initiation of the pharyngeal swallow, and oral residue. Pharyngeal phase impairments were relatively infrequent and comparatively mild, with the exception of reduced tongue base retraction contributing to pharyngeal residue, and mildly disrupted laryngeal vestibule closure. Disease severity correlated significantly with oral (r = .0.42, p = .0.002) and pharyngeal (r = 0.41, p = .0.003) total sum scores as well as with the oral phase components of oral transport (r = .0.33, p = .0.02) and initiation of the pharyngeal swallow (r = .0.38, p = .0.007), and PAS for thin liquids (r = .0.44, p = .0.001). The PSP Rating Scale was not more strongly correlated with swallowing impairment than has been reported for other disease severity rating scales. Dysphagia is a common complaint of patients with PSP. The current findings corroborate and expand upon those reported in the literature, detailing relatively more frequent and more severe oral phase impairments and relatively spared hyolaryngeal excursion. Further research is needed to characterize the progression of dysphagia in PSP and to determine whether dysphagia varies in character or in rate of progression across variants of PSP.

Numerical analysis of varies geometries on dynamic analysis on the gravity platform

On Gravity platform Dynamic Response is a support structure held in place by gravity. Given that the gravity platforms are supportedby the sea bed but not attached to the ground, the motion of them is known as a rocking fluctuation. During the fluctuations, theplatform maybe overturned if the angle is large. In this study, using Ansys Aqwa hydrodynamic software and analytical methods withregard to the performance, the dynamic interaction of platform’s geometry on hydrodynamic forces have been simulated. Theobjective of this study was to analyze the hydrodynamic parameters of the sea and rocking fluctuations of gravity platforms under theimpact of regular wave’s moment considering the soil mechanics and hydrodynamic features of the structure. In order to achievethe objective the hydrodynamic forces using numerical simulations and analytical methods for one column and three hollow columnsplatforms were analyzed. Finally, responses of the platform to irregular waves were studied using numerical simulation. The resultsshowed that with the increasing of the depth, the impact of wave’s force and moment on the base of platform are reduced throughexponential relationship. The reductions are due to the effective depth that is equal to half the wave length. The results suggestthat the response of the rocking motion of gravity platform shows significant changes in relation to height and wavelength. Based onthe curves fitted to the data of the fluctuation angle, sustainability of the platform in the rocking motion can be thoroughly andcompletely investigated.

A 3D numerical analysis of wave-induced seabed response around a monopile structure

ABSTRACT Despite the numerous ideas concept for an offshore wind turbine foundation, the monopile foundation is the most widely adopted concept in engineering practices. In this paper, a 3-dimensional integrated numerical model is established to study the wave-induced oscillatory seabed responses around a monopile foundation by adopting the Reynolds-Average Navier-Stokes (RANS) equation with turbulence closure model for the mean flow and the Biot’s consolidation equation for porous seabed as the governing equations respectively. The present wave and seabed sub-models in this studies are verified with physical experimental results and an analytical solution, while for the monopile structure, the wave impact force exerted on it are calculated and verified with physical experimental data to show that the present model has the ability to simulate the wave-seabed-pile structure interaction (WSSI-PILE). The numerical investigations on the monopile foundation indicated that the wave impact force on the pile structure and the seabed foundation has a very significant impact on horizontal displacement of the monopile within the seabed and the pile rocking motion. Parametric studies analysis on the effect of wave height, seabed permeability and pile structure diameter also indicated significant influence on the oscillatory wave-induced dynamic response .

Nonlinear Static and Dynamic Analysis of Rocking Masonry Corners Using Rigid Macro-Block Modeling

The corner failure is one of the most typical local mechanisms in masonry buildings vulnerable to earthquakes. The seismic assessment of this mechanism is poorly studied in the literature and in this paper it is addressed by means of both nonlinear static and dynamic analyses of rocking rigid blocks. The static approach is based on the displacement-based method and is aimed at predicting the onset of the 3D failure mechanism and its evolution through incremental kinematic analysis. This approach also considers the presence of a thrusting roof and the stabilizing contribution of frictional resistances exerted within interlocked walls. The capacity in terms of both forces and displacements is compared with the seismic demand through the construction of acceleration–displacement response spectra, with some originality. The nonlinear dynamic approach is based on the seminal Housner’s work on rocking rigid blocks and considers the influence of transverse walls, roof overloads and outward thrust, all included in an updated equation of one-sided motion. In particular, the process of defining an equivalent prismatic block, representative of the original corner geometry, is presented to convert the 3D dynamic problem into a 2D rocking motion. The wide suitability and advantage of such modeling approaches to assess the seismic response of rocking masonry structures with reference to specific limit states are demonstrated through a real case study, i.e. the collapse of a corner in a masonry school building during the 2016–2017 Central Italy seismic sequence. The compared results provide a good agreement of predictions in terms of both onset and overturning conditions, for which the static model appears to be more conservative than the dynamic one.

Mapping of ground motion amplifications for the Fraser River delta in Greater Vancouver, Canada

The Fraser River delta in Greater Vancouver, Canada consists of deep soft deposits of silts and clays, and it is well known that the deep soil deposits can amplify the low frequency contents of ground motions. This study aims to investigate the effects of deep soil deposits in the delta on ground motion amplifications by using thorough site response simulations that account for the full soil profiles and a suite of recorded ground motions that covers a wide range of intensity levels. Based on both equivalent-linear and nonlinear site response simulations, the effects of soil depth (represented by natural period of the soil, TS) on ground motion amplifications for various spectral periods are clearly demonstrated. The ground motion amplification maps for various spectral periods and rock ground motion intensity levels are also generated to be used in the regional seismic hazard assessment for infrastructure. It is found that ground motions for long periods are substantially amplified in the center of the delta, while those for short periods are de-amplified when input rock motions are large.

Characterization of the Metabolic Response of Streptomyces clavuligerus to Shear Stress in Stirred Tanks and Single-Use 2D Rocking Motion Bioreactors for Clavulanic Acid Production.

Streptomyces clavuligerus is a gram-positive filamentous bacterium notable for producing clavulanic acid (CA), an inhibitor of β-lactamase enzymes, which confers resistance to bacteria against several antibiotics. Here we present a comparative analysis of the morphological and metabolic response of S. clavuligerus linked to the CA production under low and high shear stress conditions in a 2D rocking-motion single-use bioreactor (CELL-tainer ®) and stirred tank bioreactor (STR), respectively. The CELL-tainer® guarantees high turbulence and enhanced volumetric mass transfer at low shear stress, which (in contrast to bubble columns) allows the investigation of the impact of shear stress without oxygen limitation. The results indicate that high shear forces do not compromise the viability of S. clavuligerus cells; even higher specific growth rate, biomass, and specific CA production rate were observed in the STR. Under low shear forces in the CELL-tainer® the mycelial diameter increased considerably (average diameter 2.27 in CELL-tainer® vs. 1.44 µm in STR). This suggests that CA production may be affected by a lower surface-to-volume ratio which would lead to lower diffusion and transport of nutrients, oxygen, and product. The present study shows that there is a strong correlation between macromorphology and CA production, which should be an important aspect to consider in industrial production of CA.

Sheep Quickstep while the Floor Rock and Rolls: Visuomotor Lateralization during Simulated Sea Travel.

Simple SummaryDuring livestock transport the floor of the vehicle moves in a way that can disturb their balance. This can stress the animals, producing signals that are processed by the right half of their brain. This half of the brain controls movement of the sheep on the opposite, left side of their body. Hence we investigated whether limb movement was more pronounced on this side, providing evidence of stress responses. We found that sheep limb movements were increased in their left hindlimb and right forelimb during balance correction when the floor movements were most unpredictable. This may be explained by sheep using their back right leg as a pivot. We further tested which side sheep lie down on from internet pictures and found a preference for left side lying. We conclude that sheep balance correction shows evidence of a preferred use of limbs, which suggests that sheep are stressed by floor motion.Unpredictable floor motions during transport disturbs animals’ balance, requiring stepping to move the centre of gravity in the direction of body movement. When repeated regularly, this may be stressful, requiring involvement of the right brain hemisphere, hence we investigated the existence of behavioral laterality in sheep during prolonged floor motions. Six sheep were restrained in pairs on a programmable rocking platform, in which they were unable to turn around. They were exposed to three continuous rocking motion treatments (roll, pitch or both) in a regular or irregular pattern for 1 h periods in a changeover design. Right forelimb and left hindlimb diagonal stepping was more frequent in response to the motion treatment of irregular roll and pitch, which previous research has suggested to be the most stressful from heart rate measurements. An overall strategy to maintain balance appeared to be the use of the right hindlimb as a stabilizer, which was repositioned least often of all limbs until towards the end of the hour of experimental treatment. Of each tested pair, sheep restrained on the left side of the rocking floor stepped significantly often than its partner restrained on the right side, and we postulate the existence of visuomotor lateralization as left restrained sheep were unable to view their partner within the field of view of their left eye. We also investigated which side sheep lie down on, which if left lateralized could explain our observed bipedal diagonal control of sheep balance under stress. From the observation of 412 web-based images of sheep, there was an overall left-sided laterality to their lying, as has been observed in cattle. We conclude that stepping activity in sheep in response to a motion stressor is lateralized, providing evidence that floor motion experienced in transport may induce stress responses.

Wear Prediction of UHMWPE Cup Against Commercially Pure Titanium Hip Implant With The Nonlinear Load and Contact Area Wear Equation

Hip implants are prostheses designed for severe hip arthritis patients. One of its components, acetabular cup is mostly made from ultra-high molecular weight polyethylene (UHMWPE). This polymer has a wear problem. Its debris would cause osteolysis followed by implant failures. Numerical studies of this problem were commonly used a linear contact pressure wear equation. Recently it was found not suitable to model the polymer wear in hip implants. This study used a nonlinear equation to predict the UHMWPE volumetric wear. It states a nonlinear relation between wear, load and contact area. The computation model was a biaxial rocking motion hip simulator assembly with UHMWPE acetabular cup sliding on commercially pure titanium femoral head. Multidirectional pin on disc experiments conducted to obtain wear factor and coefficient of friction data for the computations. Commercial finite element software calculated the other parameters. Predicted volumetric wear has a good agreement with the experimental data. Lowest numerical error was found 0.53 %.

An analysis of influence of material damping on dynamic response of surface foundation under rotational motion

ABSTRACT Material damping arises due to the soil present beneath the foundation and controls the behaviour of the foundation under dynamic excitation. In the present study, an attempt has been taken to observe the effect of soil material damping on the dynamic response of foundation under rocking and torsional motion. A recent trend in present methods of dynamic analysis of foundation in the frequency domain is to find out the dynamic impedance functions, i.e. spring coefficient and damping coefficient. For foundation under rotational motion, i.e. rocking and torsion, the material damping is introduced using the Kelvin model and the results thus obtained are compared with those obtained by Hysteretic model and Voigt model. Parameter sensitivity analysis is carried out to determine the most influencing parameter. The study suggests that foundation under rocking motion is non-linearly influenced by the Poisson’s ratio of soil.

A Sea Wave Surge Base Alignment Test Device Based on the EtherCAT Fieldbus

A sea wave surge base alignment test device consisting of a linear motion guide rail, a stewart platform, a rotating mechanism, a cantilever beam and an electronic control system based on an EtherCAT fieldbus is designed. The linear motion guide and the stewart platform provide the seven movement dimensions for the whole device. the rotating mechanism, the cantilever beam and the linear motion guide widen the movement dimension and amplitude of the device.the EherCAT fieldbus effectively satisfies the real-time, synchronization and accuracy of the whole device. the whole system effectively satisfies the requirements of multi-degree, large amplitude, low frequency, large acceleration combined superimposed rocking motion and simulation motion in the sea wave surge simulation motion.