Numerical solution of a stochastic model of a ball-type vibration absorber

summary:The mathematical model of a ball-type vibration absorber represents a non-linear differential system which includes non-holonomic constraints. When a random ambient excitation is taken into account, the system has to be treated as a stochastic deferential equation. Depending on the level of simplification, an analytical solution is not practicable and numerical solution procedures have to be applied. The contribution presents a simple stochastic analysis of a particular resonance effect which can negatively influence efficiency of the absorber

Identification of quasiperiodic processes in the vicinity of the resonance

summary:In nonlinear dynamical systems, strong quasiperiodic beating effects appear due to combination of self-excited and forced vibration. The presence of symmetric or asymmetric beatings indicates an exchange of energy between individual degrees of freedom of the model or by multiple close dominant frequencies. This effect is illustrated by the case of the van der Pol equation in the vicinity of resonance. The approximate analysis of these nonlinear effects uses the harmonic balance method and the multiple scale method

Appell-Gibbs Approach in Dynamics of Non-Holonomic Systems

Hamiltonian functional and relevant Lagrange’s equations are popular tools in the investigation of dynamic systems. Various generalizations enable to extend the class of problems concerned slightly beyond conventional limits of Hamiltonian system. This strategy is very effective, particularly concerning two-dimensional (2D) and simpler three-dimensional (3D) systems. However, the governing differential systems of most non-holonomic 3D systems suffer from inadequate complexity, when deduced using this way. Any analytical investigation of such a governing system is rather impossible and its physical interpretation can be multivalent. For easier analysis, particularly of systems with non-holonomic constraints, the Appell-Gibbs approach seems to be more effective providing more transparent governing systems. In general, the Appell-Gibbs approach follows from the Gaussian fifth form of the basic principle of dynamics. In this chapter, both Lagrangian and Appell-Gibbs procedures are shortly characterized and later their effectiveness compared on a particular dynamic system of a ball moving inside a spherical cavity under external excitation. Strengths and shortcomings of both procedures are evaluated with respect to applications

Stochastic Resonance and Related Topics

The stochastic resonance (SR) is the phenomenon which can emerge in nonlinear dynamic systems. In general, it is related with a bistable nonlinear system of Duffing type under additive excitation combining deterministic periodic force and Gaussian white noise. It manifests as a stable quasiperiodic interwell hopping between both stable states with a small random perturbation. Classical definition and basic features of SR are regarded. The most important methods of investigation outlined are: analytical, semi-analytical, and numerical procedures of governing physical systems or relevant Fokker-Planck equation. Stochastic simulation is mentioned and experimental way of results verification is recommended. Some areas in Engineering Dynamics related with SR are presented together with a particular demonstration observed in the aeroelastic stability. Interaction of stationary and quasiperiodic parts of the response is discussed. Some nonconventional definitions are outlined concerning alternative operators and driving processes are highlighted. The chapter shows a large potential of specific basic, applied and industrial research in SR. This strategy enables to formulate new ideas for both development of nonconventional measures for vibration damping and employment of SR in branches, where it represents an operating mode of the system itself. Weaknesses and empty areas where the research effort of SR should be oriented are indicated

Isotope shift in the Sulfur electron affinity: observation and theory

The electron affinities eA(S) are measured for the two isotopes 32S and 34S (16752.9753(41) and 16752.9776(85) cm-1, respectively). The isotope shift in the electron affinity is found to be positive, eA(34S)-eA(32S) = +0.0023(70) cm-1, but the uncertainty allows for the possibility that it may be either "normal" (eA(34S) > eA(32S)) or "anomalous" (eA(34S) < eA(32S)). The isotope shift is estimated theoretically using elaborate correlation models, monitoring the electron affinity and the mass polarization term expectation value. The theoretical analysis predicts a very large specific mass shift that counterbalances the normal mass shift and produces an anomalous isotope shift, eA(34S)-eA(32S) = - 0.0053(24) cm-1. The observed and theoretical residual isotope shifts agree with each other within the estimated uncertainties.Comment: 15 pages, 4 figure

GDPR in a Metaversal post-digital World: The Law of Everything or the Law of Nothing?

9. Industry, innovation and infrastructur

A combined spectroscopic and photometric stellar activity study of Epsilon Eridani

We present simultaneous ground-based radial velocity (RV) measurements and space-based photometric measurements of the young and active K dwarf Epsilon Eridani. These measurements provide a data set for exploring methods of identifying and ultimately distinguishing stellar photospheric velocities from Keplerian motion. We compare three methods we have used in exploring this data set: Dalmatian, an MCMC spot modeling code that fits photometric and RV measurements simultaneously; the FF$'$ method, which uses photometric measurements to predict the stellar activity signal in simultaneous RV measurements; and H$\alpha$ analysis. We show that our H$\alpha$ measurements are strongly correlated with photometry from the Microvariability and Oscillations of STars (MOST) instrument, which led to a promising new method based solely on the spectroscopic observations. This new method, which we refer to as the HH$'$ method, uses H$\alpha$ measurements as input into the FF$'$ model. While the Dalmatian spot modeling analysis and the FF$'$ method with MOST space-based photometry are currently more robust, the HH$'$ method only makes use of one of the thousands of stellar lines in the visible spectrum. By leveraging additional spectral activity indicators, we believe the HH$'$ method may prove quite useful in disentangling stellar signals

Rethinking Child Protection in Emergencies

The humanitarian system is struggling to adapt to changes in the global political environment, trends in armed conflict and displacement, and advances in science and technology. In recent years, the international community has undertaken a number of efforts to overcome these challenges, such as the Agenda for Humanity, a plan that outlines the changes needed to alleviate suffering, reduce risk, and lessen vulnerability on a global scale. This article reviews recent evidence from a range of disciplines to inform these efforts, especially as they relate to the protection of children. Early childhood and adolescence constitute two critical periods of child development that lay the foundations for future health and wellbeing. Exposure to adversity in crisis contexts can compromise this development, with potentially life-long consequences. Evidence suggests that relationships with caregivers and peers play a central role in mediating childhood experiences of adversity. Unfortunately, interventions for children affected by crises are usually too fragmented to maximize the protective effects of healthy relationships. This article stresses the importance of developing multisectoral and relational interventions capable of promoting healthy development across the life course. Given the central role of caregivers, the household is an especially powerful level of intervention for combining approaches from different sectors. More concerted efforts are needed to develop household interventions that combine traditional sectoral approaches with innovative, cross-cutting measures, such as cash transfers and parental support. Household interventions should also be an integral part of broader community and society level actions, which together form more comprehensive systems of care

A Ball-Type Passive Tuned Mass Vibration Absorber for Response Control of Structures under Harmonic Loading

Ball-type tuned mass absorbers are growing in popularity. They combine a multi-directional effect with compact dimensions, properties that make them attractive for use at slender structures prone to wind excitation. Their main drawback lies in limited adjustability of damping level to a prescribed value. Insufficient damping makes ball-type absorbers more prone than pendula to objectionable effects stemming from the non-linear character of the system. Thus, the structure and design of the damping device have to be made so that the autoparametric resonance states, occurrence of which depends on system parameters and properties of possible excitation, are avoided for safety reasons. This chapter summarises available 3D mathematical models of a ball-pendulum and introduces the non-linear approach based on the Appell–Gibbs function. Efficiency of the models is then illustrated for the case of kinematic and random excitation. Interaction of the absorber and the harmonically forced simple linear structure is numerically analysed. Finally, the chapter provides examples of typical patterns of the autoparametric response and outlines possibilities of applications in practical engineering

Oligomeric state study of prokaryotic rhomboid proteases

AbstractRhomboid peptidases (proteases) play key roles in signaling events at the membrane bilayer. Understanding the regulation of rhomboid function is crucial for insight into its mechanism of action. Here we examine the oligomeric state of three different rhomboid proteases. We subjected Haemophilus influenzae, (hiGlpG), Escherichia coli GlpG (ecGlpG) and Bacillus subtilis (YqgP) to sedimentation equilibrium analysis in detergent-solubilized dodecylmaltoside (DDM) solution. For hiGlpG and ecGlpG, rhomboids consisting of the core 6 transmembrane domains without and with soluble domains respectively, and YqgP, predicted to have 7 transmembrane domains with larger soluble domains at the termini, the predominant species was dimeric with low amounts of monomer and tetramers observed. To examine the effect of the membrane domain alone on oligomeric state of rhomboid, hiGlpG, the simplest form from the rhomboid class of intramembrane proteases representing the canonical rhomboid core of six transmembrane domains, was studied further. Using gel filtration and crosslinking we demonstrate that hiGlpG is dimeric and functional in DDM detergent solution. More importantly co-immunoprecipitation studies demonstrate that the dimer is present in the lipid bilayer suggesting a physiological dimer. Overall these results indicate that rhomboids form oligomers which are facilitated by the membrane domain. For hiGlpG we have shown that these oligomers exist in the lipid bilayer. This is the first detailed oligomeric state characterization of the rhomboid family of peptidases