Analysis of the lateral vibrations of an unbalanced Jeffcott rotor

This paper examines experimentally and analytically the lateral vibrations of a Jeffcott rotor running at various unbalance states. Using a Bently Nevada RK-4 rotor kit, three states of eccentric mass unbalance were assumed in this study: 0.4g, 0.8g and 1.2g. Measurements of the startup data and the steady state data at rigid and flexible rotor condition were collected using a setup that mimics the vibration monitoring industrial practices. Lagrange method was assumed to construct a linear mathematical model of the investigated rotor, based on rigid rotor assumptions, that can predict analytically the lateral vibrations. The dynamic characteristics of the system, including the linearized bearing induced stiffness, were solely extracted from startup data. It was concluded that the developed twodegrees- of-freedom model was able to predict the lateral vibration at the rigid condition with an error around 5%. Whereas it failed to predict the response at flexible condition with matching accuracy. Unlike the majority of the work done in this field where complex, nonlinear mathematical model were used to model real systems, this work validates the applicability of using simple mathematical models in predicting the response of a real rotorsystem with an acceptable accuracy.

Load Classification for Dynamic Responses on Single Mass Cantilever Structure With Bi-Linear Material Property

Nuclear Power Plants (NPPs) are designed to withstand postulated earthquake events. Seismic loads induced by a seismic event on essential structures such as a piping are typically evaluated with two different load categories: inertia loads and deformation loads which are also called as load-controlled loads and displacement-controlled loads, respectively. The inertia force is still believed to govern failure mode of piping components as almost of all design codes for NPPs give weight at qualifying the inertia loads as primary stress components for piping. The first paper PVP2015-45287 [22] anticipated a structure excited by a lower frequency than the natural frequency which is considered as an excitation at Rigid condition could result in plastic collapse because of a minimal recovering force counteracting the deformation. However, the second paper PVP2016-63363 [23] which applied an elastic-plastic analysis showed the different conclusion that a single mass cantilever structure at Rigid condition finally behaved as Soft condition which was anticipated as a stable condition in the paper along the progress of the plastic deformation on the structure. This result implies that the current design codes which assume elastic-behavior may include significant over-conservatism to ensure the adequacy of structures under seismic condition. As many experimental results are showing, very large seismic loads which excessively exceed the design limit barely caused failure in piping components. This paper investigates the relationship between inertia forces and element forces on a single mass cantilever model applying a bi-linear material property against several random time-history loads which are adjusted to represent the said excitation conditions. This paper also clarifies the correlation between deformations due to the excitations and the inertia/element forces observed on the models. This study takes over the previous researches published as PVP2015-45287 and PVP2016-63363.

Eye tracking a self-moved target with complex hand-target dynamics

Previous work has shown that the ability to track with the eye a moving target is substantially improved when the target is self-moved by the subject's hand compared with when being externally moved. Here, we explored a situation in which the mapping between hand movement and target motion was perturbed by simulating an elastic relationship between the hand and target. Our objective was to determine whether the predictive mechanisms driving eye-hand coordination could be updated to accommodate this complex hand-target dynamics. To fully appreciate the behavioral effects of this perturbation, we compared eye tracking performance when self-moving a target with a rigid mapping (simple) and a spring mapping as well as when the subject tracked target trajectories that he/she had previously generated when using the rigid or spring mapping. Concerning the rigid mapping, our results confirmed that smooth pursuit was more accurate when the target was self-moved than externally moved. In contrast, with the spring mapping, eye tracking had initially similar low spatial accuracy (though shorter temporal lag) in the self versus externally moved conditions. However, within ∼5 min of practice, smooth pursuit improved in the self-moved spring condition, up to a level similar to the self-moved rigid condition. Subsequently, when the mapping unexpectedly switched from spring to rigid, the eye initially followed the expected target trajectory and not the real one, thereby suggesting that subjects used an internal representation of the new hand-target dynamics. Overall, these results emphasize the stunning adaptability of smooth pursuit when self-maneuvering objects with complex dynamics.

Ultrafast charge transfer dynamics in supramolecular Pt(ii) donor–bridge–acceptor assemblies: the effect of vibronic coupling

Thanks to major advances in laser technologies, recent investigations of the ultrafast coupling of nuclear and electronic degrees of freedom (vibronic coupling) have revealed that such coupling plays a crucial role in a wide range of photoinduced reactions in condensed phase supramolecular systems. This paper investigates several new donor–bridge–acceptor charge-transfer molecular assemblies built on a trans-Pt(ii) acetylide core. We also investigate how targeted vibrational excitation with low-energy IR light post electronic excitation can perturb vibronic coupling and affect the efficiency of electron transfer (ET) in solution phase. We compare and contrast properties of a range of donor–bridge–acceptor Pt(ii) trans-acetylide assemblies, where IR excitation of bridge vibrations during UV-initiated charge separation in some cases alters the yields of light-induced product states. We show that branching to multiple product states from a transition state with appropriate energetics is the most rigid condition for the type of vibronic control we demonstrate in our study.

Modelling the Effect of Flexural Vibration on Sound Absorption of a Micro-Perforated Panel Using Wave Propagation Method

Micro-perforated panel (MPP) is well known as the alternative green sound absorbing material replacing the synthetic porous absorber. Several works have been established which model the sound absorption performance of the MPP with various arrangements. However, most existing models are for MPP with rigid condition and rarely discuss the effect of vibration due to the impinging sound. In this paper, a simple approach using wave propagation technique is proposed to take into account the effect of flexural wave in the MPP on its sound absorption. The model begins with an MPP coupled with a solid panel separated by an air gap. The impedance of the back solid panel can then be adjusted to a very large value to simulate a rigid wall.

Mechanisms to absorb load in amputee running

Background: We aimed to determine if a shock absorbing pylon (SAP) influenced the ground reaction force characteristics and the shock absorbing mechanisms compared to a rigid pylon (Rigid) during the loading phase in running. Objectives: To determine if the SAP influences the mechanisms of loading compared to the Rigid condition. Study Design: A convenience sample of transtibial amputees participated in a laboratory-based study. The prosthetic set-up was randomly altered fd\sdsd. Methods: Five recreationally active male transtibial amputees age: 18–50 years; mean mass: 86.7 ± 17.5 kg; height: 1.77 ± 0.07 m) volunteered from a population-based sample. They completed a within-participant-designed study assessing a SAP and a Rigid condition during running. Kinematic and kinetic data were collected during two sessions following a one-week customization period. Results: Loading rate, peak vertical and horizontal ground reaction forces and the time to each measure along with knee and hip angular displacement, absorbing powers and work done between the SAP and Rigid conditions were not systematically affected by the prosthetic condition. Conclusions: The effect of the SAP was minimal and inconsistent in the loading phase, with only some amputees presenting higher and others with lower values for the tested variables. Clinical relevance The inclusion of a prosthetic shock absorber in the form of a SAP did not systematically alter the kinetic characteristics or shock absorbing mechanisms of the residual joints. It appears that the prescription of a SAP is not justified for these recreationally active amputees.