Improving the dynamic stability of a workpiece dominated turning process using an adaptronic tool holder

In this contribution, inside turning of a thin-walled cylinder is investigated in simulation. Self-excited vibrations can arise due to repeated cutting of the same surface, that lead to instability. A flexible multibody system model of the system is the basis for a subsequent analysis of the stability of the process. Stability analysis is done using an approximation as a time-discrete system via the semi-discretization method. An adaptronic turning chisel comprising a piezo actuator and sensors is then used in combination with different control concepts to improve the stability of the process. The effectiveness of the different strategies is compared based on the influence on the stability charts. A classic H_∞ controller based on a model of the coupled system of workpiece and tool can only yield some improvements, when an additional measurement of the workpiece displacement is added. Incorporating knowledge on the cutting process coupling workpiece and tool using a gain scheduled H_∞ controller allows further improvements. However, robustness with respect to model uncertainties, notably concerning the force law, remains an issue.     

Dielectric study of ferroelectric side-chain liquid crystalline polysiloxanes with broad temperature ranges of the chiral smectic C phase 1. Structure dependence of dielectric relaxation

The dielectric behavior of a series of ferroelectric side-chain liquid crystalline polysiloxanes containing 1–3 oligooxyethylene units as spacers, and 4-(S)-2-methyl-1-butyl[[[(4-hydroxy-biphenyl-4′-yl)]carbonyl]oxy] benzoate or 4-(S)-2-methyl-1-butyl[[(4-hydroxy-biphenyl-4′-yl)carbonyl]oxy]-3-fluoro benzoate side groups was studied by broadband dielectric spectroscopy. The increase of the spacer length, and incorporation of a strong dipole moment fluoro-substituent into the mesogenic group, resulted in a decrease of the relaxation activation energy and an increase in the intensity of the relaxation. Moreover, the relaxation peak of the Goldstone mode has only been observed for the FLCP with a lateral fluoro-substituent. The relationship between the thermal dynamic behavior and chemical structure is discussed in detail. Furthermore, analysis of the dielectric relaxation behavior of these FLCPs showed that the molecular relaxations could be described by the Cole-Cole equation. © 1996 John Wiley & Sons, Inc.     

Damping Identification Using Perturbation Techniques and Higher-Order Spectra

Perturbation techniques and spectral moments are combined tocharacterize and quantify the damping and nonlinear parameters of thefirst mode of a three-beam two-mass frame. The frame is excitedharmonically near twice its lowest natural frequency. The response ismodeled with a second-order nonlinear equation with quadratic and cubicterms and linear and quadratic damping terms. The method of multiplescales is used to obtain a second-order approximate solution for thismodel. Bispectral analysis is used to quantify the level of couplingbetween modes and measure their phase difference. The amplitudes andphase difference between the excitation and response mode with differentfrequencies are substituted into the approximate solution to determinethe damping and nonlinear parameters.     

八级形变系统的集体运动

利用一组内部坐标和三个欧拉角描述八极形变系统的集体运动,动能被分解成三部分:体坐标系下的形变振动,体坐标系围绕实验室系的转动以及振动和转动的耦合.量子化的动能算符被导出,一些特殊八极形变下的集体谱被讨论.     

Calculation of Normal Vibrations of the Tetraazaporphin Molecule and Interpretation of Quasiline Spectra

Quasiline fluorescence and fluorescence-excitation spectra of tetraazaporphin and its N-deuterated derivative in n-octane at 77 K have been investigated, and the frequencies of normal vibrations in electronic states S ₀ and S ₁ have been determined. Calculation of normal vibrations of these molecules has been done and, on its basis, the experimental data are interpreted. It is shown that in the spectra, predominantly the totally symmetric vibrations of type A _g symmetry of the point D _2h symmetry group are active. Some activation of the nontotally symmetric B _1g vibrations in the fluorescence-excitation spectra is explained by the nonadiabatic interaction of the vibrational sublevels of the excited electronic state S ₁ with the purely electronic level S ₂.     

Shape Coexistence in Odd-Mass Nuclei near Z = 50

An earlier work dealing with shape coexistence for even-even nuclei is extended to treating odd-mass nuclei including proton excitations across closed shell. With the approach, energy spectra and some E2 transition branching ratios are calculated for odd-Anuclei^113~125Sb,^115~127I. The theoretical results give a good reproduction to the experimental data.     

Spectra and E2 Transition Rates in 116-132X in the IBM

The positive-parity collective states in the even-even ^116-132Xe isotopes are studied in the framework of the interacting boson model. It is found that the isotopes can be well described by a schematic Hamiltonian in transition from U(5) to SU(3) dynamical symmetry. As the valence neutron number changes, the structure of the isotopes shows regular patterns of change.     

Minimal Developmental Computation: A Causal Network Approach to Understand Morphogenetic Pattern Formation

What information-processing strategies and general principles are sufficient to enable self-organized morphogenesis in embryogenesis and regeneration? We designed and analyzed a minimal model of self-scaling axial patterning consisting of a cellular network that develops activity patterns within implicitly set bounds. The properties of the cells are determined by internal ‘genetic’ networks with an architecture shared across all cells. We used machine-learning to identify models that enable this virtual mini-embryo to pattern a typical axial gradient while simultaneously sensing the set boundaries within which to develop it from homogeneous conditions—a setting that captures the essence of early embryogenesis. Interestingly, the model revealed several features (such as planar polarity and regenerative re-scaling capacity) for which it was not directly selected, showing how these common biological design principles can emerge as a consequence of simple patterning modes. A novel “causal network” analysis of the best model furthermore revealed that the originally symmetric model dynamically integrates into intercellular causal networks characterized by broken-symmetry, long-range influence and modularity, offering an interpretable macroscale-circuit-based explanation for phenotypic patterning. This work shows how computation could occur in biological development and how machine learning approaches can generate hypotheses and deepen our understanding of how featureless tissues might develop sophisticated patterns—an essential step towards predictive control of morphogenesis in regenerative medicine or synthetic bioengineering contexts. The tools developed here also have the potential to benefit machine learning via new forms of backpropagation and by leveraging the novel distributed self-representation mechanisms to improve robustness and generalization.     

Correlated Nucleon Pair Model and Microscopic Basis of Interacting Boson

An earlier work dealing with low-lying collective states in nuclei is revised and improved. Correlated and independent nucleon S and D pairs properly modified so that they behave approximately like bosons are constructed in terms of which a model space for lowlying collective states is defined, and a microscopic basis for IBM is thus set up. All dynamical variables can also be "bosonized", i.e., expressed in terms of these "bosons" but with statedependent coefficients or operators to incorporate their state dependence in model space.     

The Structure of S Pair in Collective States (Ⅰ)

A new S pair and seniority particle operator used to overcome the difficulties due to seniority mixing are defined in collective motion of nuclei. The structure amplitude of S pair is determined in a self-consistent manner.