Excessive Acceleration Research Articles

Speed excess and total acceleration: a kinematical approach to entanglement

Abstract The total variance of a spin state is defined as the average of the variances of spin projection measurements along three orthogonal axes. We show that this quantity also gives the squared rotational speed of the state in projective space, averaged over all rotation axes. We compute the addition law, under system composition, for this quantity and find that, in the case of separable states, it is of simple pythagorean form. In the presence of entanglement, we find that the composite state "rotates faster than its parts", thus unveiling a kinematical origin for the correlation of total variance with entanglement. We analyze a similar definition for the acceleration of a state under rotations, for both pure and mixed states, and probe numerically its relation with a wide array of entanglement related measures.

Numerical simulation of different aircraft sub-floor structures during ditching

AbstractTo enhance the impact resistance capacity and ensure the floatability of aircraft after ditching, the slamming response of three types of aircraft sub-floor structures are investigated including the flat, cylindrical and ellipsoidal under floor. A coupled Finite Element-Smooth Particle Hydrodynamic (FE-SPH) method is employed with focus on non-linear structural collapse in fluid-structure interaction. The material is defined by bilinear elastic plastic law, and the strain rate effect is taken into account. Further, comparison and analyses are performed in terms of acceleration, local pressure and strains at different speeds. Results show that conventional flat sub floor structures perform poorly during ditching due to excessive peak acceleration and pressure. By contrast, the peak acceleration of ellipsoidal under floor is lower at all measured speeds and the pressure on the sides is reduced. Moreover, the ellipsoidal sub-floor with bi-directional curvature generates smaller plastic strain and deflection of skin, demonstrating better mechanical properties in water impact scenarios.

Numerical study on the motion characteristics of free fall lifeboats entering calm water and rough sea

As ocean engineering operations extend into deeper seas, the working environment becomes increasingly complex, making free fall lifeboats (FFLBs) more vital for maritime disaster rescues. Unlike traditional davit-launched lifeboats, FFLBs are propelled into the water at a specific velocity and angle, engaging in a complex motion process of launch, impact, submersion, and resurfacing. Therefore, to assess the safety of FFLBs, this paper regarding the lifeboat as a rigid body aims to investigate the six-degree-of-freedom motion characteristics of lifeboat entering the water with different entry angles θ and wave environment, with a specific focus on analyzing the primary causes of capsizing. The numerical simulations of water entry with various θ, wave heights H, and relative entry positions are carried out by combining large eddy simulation and overset mesh technology. The free surface is captured by the volume of fluid method, and the attitude change, acceleration change, motion trajectory, and free surface evolution law of lifeboats are analyzed. The findings suggest that lifeboats can enter calm water safely at θ of 20°–50° and maintain a stable posture. Moreover, in extreme conditions where θ is either 0° or 90°, there is a high risk of entry failure due to excessive vertical acceleration and poor motion attitude, respectively. Furthermore, when facing waves, lifeboats experience reduced horizontal displacement when entering at peak and downward zero point compared to calm water conditions, which poses challenges for avoiding potential dangers.

Vertical Track–Bridge Interaction in Railway Bridges with Ballast Superstructure: Experimental Analysis of Dynamic Stiffness and Damping Behavior

Realistic vibration predictions of railway bridges during high-speed train crossings require reliable dynamic input parameters for the applied calculation model. In particular, the dynamic stiffness and damping properties of the ballast superstructure for the mathematical consideration of the vertical track–bridge interaction (TBI) significantly influence the generated calculation results. However, due to a striking scattering of model-related characteristic values available in the literature, adequate and realistic consideration of the dynamic properties of the vertical TBI in vibration predictions is associated with considerable uncertainties. This uncertainness illustrates the need to determine experimental-based and reliable characteristic values. For targeted and isolated research of dynamic characteristics of vertical TBI, a unique large-scale test facility was developed at the Institute of Structural Engineering at TU Wien, which replicates a section of ballast superstructure on a railway bridge on a scale of 1:1 and excited to vertical movements. This paper presents the essential results and findings from the experiments, focusing on determining the ballast superstructure’s dynamic stiffness and damping characteristics, which can subsequently be implemented in practical applications for vibration predictions. As a result of the experiments, model-related dynamic stiffness and damping parameters are provided to describe the vertical TBI. In addition, the experiments are used to identify destabilization processes occurring in the ballast superstructure as a result of vertical vibrations. The investigations include the vertical TBI’s displacement and acceleration behavior and the track’s settlement behavior due to the entire structure’s vertical movements. These investigations allow for assessing the currently valid, internationally, and nationally normatively prescribed permissible accelerations for railway bridges due to train crossings. The conclusion is that short-term excessive vertical accelerations of the ballast superstructure caused by train passage do not destabilize the ballast bed or considerably change the track position.

An Image-Domain Deep-Learning Denoising Technique for Accelerated Parallel Brain MRI: Prospective Clinical Evaluation

Abstract Background Parallel imaging can accelerate MRI acquisitions, but excessive accelerations can introduce amplified noise and aliasing artifacts. Purpose To evaluate a vendor-agnostic AI-based approach to remove image degradation artifacts in highly-accelerated MRI scans, improving image quality and reducing scan time. Materials and Methods Training was performed by retrospectively degrading standard accelerated images. Evaluation was performed with both retrospective and prospectively-collected highly-accelerated images. Retrospective data were taken from ∼2000 MRI studies obtained between August 2016 and October 2022, and prospective data were collected in > 200 subjects between June and November 2022, using scanners from multiple vendors and locations. Scan time data were collected from prospective studies and used to compute time savings per sequence and per protocol for each vendor. Images were evaluated qualitatively by five board-certified radiologists and quantitatively by assessing noise, contrast and spatial resolution. Paired Wilcoxon signed-rank tests were used to compare model outputs to model inputs and low-acceleration images. Results Images from 101 adults from 5 sites and 6 scanner models from different vendors were enrolled. 89% of imaged subjects had noteworthy imaging features or pathology. Model outputs were rated superior to model inputs (p < 0.001) and most were either non-inferior (p inf > 0.05) or superior (p sup < 0.05) to baseline images in qualitative metrics of image quality and feature visibility. Quantitative evaluation of signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) improved for model outputs compared to inputs (p < 0.001) or baseline images (p < 0.005). Apparent resolution measured using the full width at half maximum or minimum (FWHM) was either enhanced (p sup < 0.05) or preserved (non-superior p sup > 0.05 and non-inferior p inf > 0.05). The scan time was reduced by an average of 29% (19%-41% per sequence). Conclusion This vendor-agnostic AI-based method achieved robust scan time savings without loss of image quality, potentially allowing for reduced cost and improved patient experience.

Reasons for Barries in Family-School Cooperation

The concept of family-school cooperation was proposed very early, and its importance has always been emphasized. However, due to the excessive acceleration of the life cycle and the extension of working hours, families have unilaterally delegated the responsibility for children's education to schools. This negative situation for student growth needs to be reversed. Families must realize that the role of the school is to complement the work initiated by the family, not to replace it. Schools also need to realize that without the cooperation of families, school functions and outcomes will be limited. However, awareness is not enough, it is necessary to know the causes of this phenomenon. Therefore, this paper conducted a systematic review of previously published research on the causes of barriers to family-school cooperation. Based on Bronfenbrenner's ecological systems theory and Epstein's overlapping spheres of influence theory, the reasons for obstacles in family-school cooperation will be analyzed from different perspectives

Vestibular hair cells are more prone to damage by excessive acceleration insult in the mouse with KCNQ4 dysfunction

KCNQ4 is a voltage-gated K+ channel was reported to distribute over the basolateral surface of type 1 vestibular hair cell and/or inner surface of calyx and heminode of the vestibular nerve connected to the type 1 vestibular hair cells of the inner ear. However, the precise localization of KCNQ4 is still controversial and little is known about the vestibular phenotypes caused by KCNQ4 dysfunction or the specific role of KCNQ4 in the vestibular organs. To investigate the role of KCNQ4 in the vestibular organ, 6-g hypergravity stimulation for 24 h, which represents excessive mechanical stimulation of the sensory epithelium, was applied to p.W277S Kcnq4 transgenic mice. KCNQ4 was detected on the inner surface of calyx of the vestibular afferent in transmission electron microscope images with immunogold labelling. Vestibular function decrease was more severe in the Kcnq4p.W277S/p.W277S mice than in the Kcnq4+/+ and Kcnq4+/p.W277S mice after the stimulation. The vestibular function loss was resulted from the loss of type 1 vestibular hair cells, which was possibly caused by increased depolarization duration. Retigabine, a KCNQ activator, prevented hypergravity-induced vestibular dysfunction and hair cell loss. Patients with KCNQ4 mutations also showed abnormal clinical vestibular function tests. These findings suggest that KCNQ4 plays an essential role in calyx and afferent of type 1 vestibular hair cell preserving vestibular function against excessive mechanical stimulation.

Совершенствование системы защиты от юза пассажирского электровоза

Objective: improving algorithms for protection against skidding and slipping using new methods for detecting excessive slipping of locomotive wheel pairs, allowing for early detection of the moment of loss of adhesion. Methods: the effectiveness of an anti-skid system is largely determined by the reliable detection of the occurrence of excessive wheel slip. Solving this problem requires the development of methods for isolating signals from the angular velocity of rotation and angular acceleration of the wheelset, taking into account dynamic processes in the mechanical part of the locomotive and interference in the measurement channel. Therefore, the article discusses the issues of processing rotation speed signals, extracting information about the amount of excess slip and angular acceleration of the wheelsets for use in anti-skid and skidding systems. One of the criteria that can improve the reliability of skid detection is proposed to use the “Estimated time before wheel locking”. Its value allows you to define the estimated time before the wheel jams (stops rotation). The introduction of this criterion makes it possible to more accurately determine the risk of a complete stop of wheelset rotation and increases the reliability of determining the occurrence of skidding. Results: it has been established that to eliminate errors in the measurement channel and isolate the signal about the angular acceleration of the wheelset in conditions of the presence of oscillations caused by the presence of the effects of the spatial dynamics of the locomotive, it is advisable to use a discrete Kalman filter. Signal processing using a Kalman filter in the presence of a reference signal makes it possible to significantly reduce the influence of spatial vibrations of the undercarriage of an electric locomotive when moving along a track with irregularities on the extracted signals of the angular velocity of rotation and angular acceleration of the wheelset. This makes it possible to reduce response thresholds and identify skidding and skidding before significant excess slip occurs. Practical importance: the necessity of using complex criteria based on the analysis of not only the slipping speed of wheelsets, but also angular accelerations, is shown to identify excessive slipping of locomotive wheelsets. Their use in the locomotive control system makes it possible to detect loss of adhesion in the early stages of slipping and skidding and improve the use of the adhesion weight of locomotives

Biological Age as a New Risk Factor for Diabetic Retinopathy in Patients with Type 2 Diabetes Mellitus

For the prevention of diabetic retinopathy, it is important to study risk factors, among which, along with the duration of type 2 diabetes mellitus, the level of glycemia, obesity, chronological age is indicated, but biological age is not considered as a potential risk factor, although biological age more objectively than chronological characterizes pathological changes at the cellular level and processes apoptosis. Purpose: to study biological age as a new risk factor for diabetic retinopathy in patients with type 2 diabetes mellitus. 580 patients aged 45–59 years with diabetic retinopathy and type 2 diabetes mellitus, whose biological age was calculated according to the Voitenko V.P. et al. methodology, took part in the study on the basis of the S.N. Fedorov National medical research center “MNTK Eye Microsurgery”. The correspondence of biological and chronological age was established in 124 patients, the excess (acceleration) of the chronological biological age in 357 patients and the excess of the biological chronological age in 99 patients. In the subsequent analysis, the first two groups were considered. Among 45–59­year­old patients with type 2 diabetes mellitus, the incidence of diabetic retinopathy was 19.82 ± 1,32 cases per 100 examined, which is statistically significantly higher (p < 0.001) compared to patients of the same age with type 2 diabetes mellitus with a chronological biological age — 10.24 ± 1.51 cases per 100 examined. Significant differences in the compared groups were also revealed in the values of the chronological age of diagnosis of diabetic retinopathy in this endocrine disease — 47.69 ± 1.24 years in patients with accelerated biological age and 50.23 ± 0.92 years in patients with matching biological and chronological age (p < 0.01). The biological age of diagnosis of diabetic retinopathy, respectively, was 56.13 ± 0.83 years and 49.61 ± 1.11 years (p < 0.001). The difference in the development of diabetic retinopathy in patients 45–59 years old with type 2 diabetes mellitus by biological age was 6,52 ± 1,24 years among patients with accelerated biological age and 0.62 ± 0.09 years among patients with matching biological and chronological age (p < 0.001). Consequently, the acceleration of biological age is a significant and new risk factor for diabetic retinopathy in patients aged 45–59 years with type 2 diabetes mellitus.

Accelerated decline in motor suppression in patients with cerebrovascular disorders: A kinetic analysis using the square-tracing task.

Patients with cerebrovascular disorders (CVDs) tend to exhibit impulsive behaviour without controlling their movements, leading to difficulty in performing activities of daily living and an increased risk of accidents. This hastiness, termed 'pacing impairment', has been studied but is not fully understood. To experimentally examine the kinetic features of pacing impairment by focusing on changes in speed and investigating neuropsychological substrates. We instructed 53 inpatients with CVDs, 20 orthopaedic inpatients, and 20 healthy participants to trace a 200 mm-sided square as slowly as possible for 120 seconds. We measured the tracing length and mean acceleration and examined the relationship between these measurements, neuropsychological symptoms, and lesion sites. Gradual acceleration in drawing, i.e., decline in motor suppression, was observed more frequently in the CVD group than in the control groups. Excessive acceleration was associated with unilateral spatial neglect, frontal lobe signs, and attention disorders but not with motor impersistence. Additionally, the incidence of excessive acceleration did not differ between left and right hemisphere lesion subgroups and was not associated with any specific lesion site. Pacing impairment can manifest as general or holistic deficits in attentional function widely distributed throughout the cerebral hemispheres.

Time-to-go based three-dimensional multi-missile spatio-temporal cooperative guidance law: A novel approach for maneuvering target interception

This research presents a novel approach called 'Time-to-target-based multi-missile spatio-temporal cooperative guidance' This approach enables the simultaneous guidance of multiple missiles, allowing them to intercept a maneuvering target from different terminal intercept angles to maximize damage. The article introduces a finite-time optimal cooperative guidance technique to reduce the load on missile engines in the line-of-sight (LOS) direction. It proposes a time-varying sliding mode guidance scheme, which is parameterized by the remaining flight time, for both longitudinal and lateral LOS directions. The scheme helps prevent excessive initial acceleration in the longitudinal and lateral LOS directions while ensuring intercept angle constraints. The time-varying cooperative guidance law proposed in this study enables the simultaneous interception of a maneuvering target with different terminal intercept angles at the moment of terminal intercept. The numerical simulation results indicate that the multi-missile spatio-temporal cooperative guidance method is effective, superior, and robust. The method enables multiple missiles to achieve the minimum acceptable intercept distance at different terminal intercept angles while optimizing fuel in the LOS direction.

Experimental investigation of dynamic behaviour of pile-supported bridges in sandy deposits

This paper presents the results of centrifuge tests performed on reinforced concrete (RC) pile–supported simply supported girder bridge models in non-liquefiable (unsaturated) and liquefiable (saturated) slightly inclined sandy soil sites. The main objectives were to investigate the dynamic response characteristics of RC pile–supported simply supported girder bridges in non-liquefiable and liquefiable soils, examine the mechanisms causing beam collapse and damage to pile–pier yielding, and verify the effectiveness of cable restrainers. The centrifuge tests were conducted in non-liquefiable and liquefiable sites, each consisting of a three-span RC pile–supported simply supported girder bridge model and a control model with a superstructure equipped with a cable restrainer. First, the dynamic characteristic parameters of the soil and structural models in both sites were obtained. Subsequently, the conventional test results were interpreted, including the excess pore pressure ratio, acceleration, and displacement. The analysis included examining the moment demand of the pile–pier structure and seismic damage mechanisms. Finally, a correlation analysis was performed to evaluate the inertial and kinematic effects on the moment demand of the pile–pier structure. The results show that the acceleration response after soil liquefaction at the inclined sites is amplified unilaterally in the downslope direction and spikes appear. The liquefiable foundation is displaced to the downslope. However, major earthquake induces foundation displacement, and liquefaction leads to a longer duration and more significant soil displacement. The installation of cable restraints significantly increased the acceleration response of the superstructure. Still, it effectively reduced the relative displacement of the superstructure and prevented the beam from collapsing. Soil liquefaction decreases the bending moment of the pile–pier structure, and the cable restrainer causes the damage mode of the pile–pier structure to shift from the pile head to the pier bottom. In the non-liquefiable scenario, the bending moment demand at the pile head has a more significant influence on the inertial effect. Additionally, using the cable restrainer system can increase the kinematic effect after liquefaction. The test results can be used to validate numerical models and provide a reference for pile foundation design.

Seismic response of the anchored frame beam reinforced slopes in seasonally frozen regions: Shaking table test and numerical analysis

Frame beam-anchor geotechnical structures are increasingly utilized to reinforce slopes in earthquake prone areas. Their dynamic responses have been thoroughly explored. However, the influence of seasonal variation in seasonally frozen regions has been largely ignored. This paper investigates the seismic response of slopes reinforced with anchored frame beams, considering the combined effects of seasonal change and earthquakes. This is achieved through a series of shaking table tests and numerical simulations. The findings reveal that the seismic responses, including acceleration response and displacement response, are more pronounced in the warm season than in the cold season. Conversely, the total axial force of the anchors and the bending moment of the frame columns are greater in the cold season. During the warm season, the frame-anchor slope support system exhibits “high-frequency filtering and low-frequency amplification”, while the spectral characteristics in the cold season are reversed. Thus, in the seismic design of such systems in seasonally frozen regions, it is crucial to consider slope deformation in the warm season to prevent damage from excessive acceleration or displacement. Additionally, the internal forces of the anchor frame structure must be checked in the cold season to avoid mechanical failures due to the combined impact of earthquakes and freezing effects. These insights offer valuable recommendations for improving the seismic design of frame beam-anchor structures in seasonally frozen regions and pave the way for further research on the seismic responses of various retaining slope structures in these areas.

Identifying Risk Factors for Preexisting or Developing Low Back Pain in Youth, High School, and Collegiate Lacrosse Players Using 3-Dimensional Motion Analysis.

Low back pain (LBP) is a common condition that can affect athletes of all ages. The risk factors for LBP onset and worsening associated with the lacrosse shooting motion are not yet known. To identify training and biomechanical factors associated with preexisting LBP and development of LBP over 6 months in youth, high school, and collegiate lacrosse players. Case-control study; Level of evidence, 3. A total of 128 lacrosse players were enrolled in this study between January 2016 and January 2019. Player characteristics, lacrosse experience, and participation in other sports were self-reported. At baseline and 2-, 4-, and 6-month follow-ups, the players self-rated the presence and severity of LBP using a numeric pain rating scale (0-10 points). Participants were grouped according to LBP symptoms: no LBP at any time point (n = 102), preexisting LBP (n = 17), or developed LBP within the 6-month period (n = 9). The lacrosse shooting motion was captured via 3-dimensional motion analysis, and kinematic and kinetic variables were recorded. A Low Back Stress Index was used to estimate lumbar stress as a function of pelvic acceleration at the time of maximum lateral trunk lean during the shot. Univariate analyses of covariance and logistic regression models were used to address study aims. Compared with the no-LBP group, the preexisting LBP group demonstrated 13.9% to 22.9% lower maximum angular velocities at the pelvis, trunk, and shoulders in the transverse plane (P < .05), 19.3% less collective pelvis-shoulder rotation in the transverse plane (P = .015), and 4.5% more knee flexion excursion (P = .063). The developed-LBP group produced 2.3% to 11.1% higher angular velocities in the pelvis, trunk, and shoulder and generated maximum pelvic acceleration values 36% to 42% higher than the remaining groups (P < .05 for both). Mean Low Back Stress Index values were not statistically significant among the groups (no LBP: 12,504 ± 13,076 deg2/s2; preexisting LBP: 8808 ± 10,174 deg2/s2; developed LBP: 19,389 ± 13,590 deg2/s2; P = .157). Preexisting LBP was associated with significantly restricted motion of the pelvis, trunk, and shoulders during a lacrosse shot. Excessive pelvic acceleration may be related to the development of LBP in lacrosse players.

Evaluation and Performance Testing of Eccentric Rolling Isolation System

Seismic isolation has become a widely accepted method for the protection of structures and nonstructural components. However, this control strategy is unfavorable against near-fault earthquakes, particularly those featuring velocity-pulse effects. Excessive isolation displacements and accelerations can occur during such earthquakes, resulting in amplified responses of the superstructure. To resolve this problem, this study develops a prototype of the eccentric rolling isolation system consisting of one platform eccentrically pin-connected to four circular rollers. The eccentric pin connection yields a nonlinear restoring force of the proposed system and results in displacement-dependent resonances, and the inherent mechanical friction also yields an energy dissipation capability of the system. As the magnitude of ground excitation increases, the prototype system generates a lower resonant frequency away from the dominant frequencies of earthquakes. This behavior is experimentally investigated and verified for mechanical behavior and seismic performance. In the experiment, sinusoidal, far-field, and near-fault ground motions are considered in shaking table testing. Some parameters, such as the eccentricity, roller size, and inertial force, are also experimentally investigated. As found in the experimental result, the feasibility of the prototype system is successfully verified. Meanwhile, the comparable simulation results further validate the mathematical model of the prototype system. Consequently, the eccentric rolling isolation system has demonstrated isolation effectiveness against far-field ground motions and has good potential to perform better than a linear system under near-fault ground motions.

Concurrent process and feedrate scheduling with convoluted basis functions and its application to fluid jet polishing

Non-traditional laser and fluid jet processes exhibit time-dependent material removal characteristics. The feedrate profile must be planned carefully along the toolpath for accurate surface profile generation while ensuring that the kinematic limits of machine tools are not violated. Conventional methods iteratively solve a deconvolution/convolution problem on the dwell-time density (reciprocal of the feedrate profile) that is computationally heavy, may leave significant residual processing errors, and even generate infeasible feed profiles with the manufacturing equipment. This paper proposes a novel approach that fully addresses the shortcomings above. Dwell-time density is first expressed as a continuous B-spline profile. The associated dwell basis functions (DBF) are convolved with the process influence function (PIF) to generate new process basis functions (PBF). This approach conveniently allows the posing of the problem as a concurrent linear least-squares problem on the control points shared by the DBFs and PBFs while ensuring the numerical stability of the solution and smoothness of the feed profile. To mitigate excessive acceleration peaks and any ringing effect around the edges of the toolpath, this paper also presents methodologies for stabilizing the scheduled feedrate profile by introducing knot vector adjustments (adaptive knot dropping) and linear edge constraints. The effectiveness of the proposed method is demonstrated and validated through simulation case studies and experimentally in fluid jet processing of precision optics. Results indicate that the proposed technique overcomes the limitations of conventional strategies and allows high-frequency surface components beyond the first zero-power frequency of the process footprint to be tracked while still generating a smooth feed profile within the acceleration limits of a machine tool. This ability stems from the localization characteristics associated with the basis functions. By improving the accuracy of high-frequency components, the proposed method exhibits the potential to fabricate topographies with sharper edges, which has been a challenge for conventional techniques.

Exploit the study of the scenarios for the control of the response of single-degree-of-freedom systems with bumpers

In earthquake-prone areas, seismic isolation systems are designed to preserve structural safety and prevent occupants’ injury and properties’ damage. However, seismically isolated structures can be subject to large displacements relative to the ground under earthquakes, which lead to define two problems, the first problem concerns to excessive displacements, whereas the second problem relates to excessive accelerations that occur when the displacements are limited by an obstacle with high relative stiffness. An arrangement that favors the solution of these problems is an appropriate interposition between the isolated structure and the obstacle of the shock absorbers or bumpers. The aim of this paper is to investigate, via numerical parametric analyses, the possibility to exploit the occurrence of impact in a two-sided vibro-impact isolated single-degree-of-freedom (SDOF) system under harmonic base excitation with beneficial effects. Through the analysis of the response scenarios which can occur varying the obstacles’ parameters, that is the width of the gap and the mechanical (stiffness and damping) properties, the target is to reduce both the maximum value of the displacement and of the acceleration of the mass, compared to the free flight condition, without possibly reducing the vibration isolation frequency range. This research path leads to the definition of vibro-impacting control systems and to the free and constrained single and multi-objective optimal design of the control system consisting of the integrated assembly of the isolation system, bumpers and gaps. The main results obtained consist in having (i) found a unique optimality condition, (ii) calculated the dissipated energy and given an energetic interpretation to the optimality condition (iii) built maps, that allow to advance behavior predictions, provide indications on the design and allow to make evaluations of the performance of the vibro-impacting system as a function of the stiffness and damping parameters and of the width of the gap. The stiffness ratio and the damping ratio, which define the mechanical properties of the bumpers, are such that the dimensionless relaxation time is about 1, (iv) finally the results are compared to multi-objective optimal design. Ultimately, the advantages of this new isolation system are: (1) provide a physical limit switch to the isolation system in order to limit the maximum displacement of the mass; (2) reduce the effects of amplification dynamics in the resonance zone; (3) reduce the static displacement, all without possibly modifying the dynamic response in the isolation zone.

Effect of damper mass on soil-structure displacement in dynamic response to earthquake vibration with finite element modelling

Earthquake is a natural disaster that always occur inside the region of pacific ring of fire. Many structures such as high-rise buildings, bridges, dams and many more failed and take severe damage due to the impact of the strong vibration of the earthquake. A pile foundation is a type of deep footing which is suitable for high-rise buildings founded on clay soils where its function to prevent potential failures such as bearing capacity and collapse. In addition, the problem of tall buildings is prone to sway and damaged when earthquake strike and such vibrations cause the dynamic behaviour of structure to change significantly in terms of excessive lateral displacements and accelerations. Thus, the effect of damper mass on soil-structure displacement in dynamic response to earthquake vibration was determined. The effectiveness of vibration absorber to the single pile structured in clay soil was modelled and simulated in finite element program PLAXIS 3D version 20 with and without the presence of the damper where the inputs were taken from the Sumatera and Chi – chi earthquakes. The problem was modelled and simulated by drawing a geometry, assigning the soil and pile materials input, loading and boundary conditions, meshing generated and staged construction for calculations of displacement structure output in response to dynamic due to earthquake vibration. The displacement-time with the effect of mass of the vibration with and without absorber are presented. The results show a good performance of damper on the single pile structured on soft soil with different types of earthquakes.

Análise dinâmica de uma laje aliviada biaxial submetida a ações humanas

Abstract The bi-axial hollow slab is the result of applying a technology that removes concrete from the least useful region and replaces it with hollow plastic spheres. This technique leads to material economy and self-weight saving, without considerable inertial loss, enabling larger and more flexible spans. Consequently, these spans are vulnerable to unwanted vibrations and dynamic acceleration caused by external actions, such as movements produced by human activity. This way, understanding the dynamic behavior of this technology and confronting it with normative limits on the project phase is essential for a good performance in the serviceability limit state, bringing comfort to the user. This paper studies the dynamic behavior of a bi-axial hollow slab submitted to human actions, such as jumping, dancing, clapping, moving the body, and moving and clapping at the same time. For that, this work made a numerical model of the structure and applied dynamic actions to it. The numerical results show that, for most of the actions, normative limits are satisfied, but the slab presents excessive accelerations in the case of jumping and dancing.

Effects of Apex Size on Dissolution Profiles in the USP II Paddle Apparatus

The use of apex vessels may solve coning problems associated with dissolution testing. However, excessive dissolution acceleration can reduce the discriminatory power. This study aimed to clarify how different apex vessel sizes affect the dissolution behavior of cone-forming formulations. Five apex vessels with different heights, centralities, and compendial vessels were used. The paddle rotation speed at which the coning phenomenon resolved was measured using standard particles of different densities. Three model formulations—USP prednisone tablets, atorvastatin calcium hydrate tablets, and levofloxacin fine granules—were selected, and dissolution tests were conducted at 30–100 revolutions per minute (rpm). Compared to the compendial vessels, the disappearance of standard particles at the apex base at lower paddle speeds in apex vessels was observed. Standard particles tended to remain in the center of the apex vessels and disappear at rotational speeds comparable to those of the compendial vessels. Dissolution increased in an apex height-dependent manner in the model formulations, except for the atorvastatin calcium hydrate tablets at 50 rpm. For levofloxacin fine granules, dissolution was also improved by reducing the paddle agitation speed to 30 rpm in the compendial vessels. Differences in apex centrality by 3 mm did not affect the dissolution rate. Our results indicate that apex vessels with low apex heights have a mount-resolving effect, but the degree of dissolution improvement by avoiding the coning phenomenon depends on the formulation characteristics used in the dissolution tests.Graphical abstract