Configuration Coordinates Research Articles

Rapid motion capture of mode-specific quantum wave packets selectively generated by phase-controlled optical pulses

Rapid motion capture of phase-controlled wave packets was realized using a sensitive wave-packet spectrometer, which was previously developed by the present authors. Two-dimensional Fourier-transformed spectrograms obtained by the wave-packet spectrometer provide us full information about the wave-packet motion on both excited- and ground-state potential surfaces. Vibrational wave packet associated with a twisting mode in a DTTCI molecule was observed to be dependent on the pulse chirp, and was generated in the excited state preferably with negatively chirped excitation. The result indicates that the excited-state wave packet can be driven along a favorable configuration coordinate by using phase-controlled femtosecond pulses. The present method is essential to adaptive coherent-control application.

Virtual-Holonomic-Constraints-Based Design of Stable Oscillations of Furuta Pendulum: Theory and Experiments

The Furuta pendulum consists of an arm rotating in the horizontal plane and a pendulum attached to its end. Rotation of the arm is controlled by a DC motor, while the pendulum is moving freely in the plane, orthogonal to the arm. Motivated, in particular, by possible applications for walking/running/balancing robots, we consider the Furuta pendulum as a system for which synchronized periodic motions of all the generalized coordinates are to be created and stabilized. The goal is to achieve, via appropriate feedback control action, orbitally exponentially stable oscillations of the pendulum of various shapes around its upright and downward positions, accompanied with oscillations of the arm. Our approach is based on the idea of stabilization of a particular virtual holonomic constraint imposed on the configuration coordinates, which has been theoretically developed recently. Here, we elaborate on the complete design procedure. The results are illustrated not only through numerical simulations but also through successful experimental tests.

Electron−Phonon Coupling in Phenyleneethynylene Oligomers: A Nonlinear One-Dimensional Configuration-Coordinate Model

In many conjugated polymers, coupling of the torsional motions to the electronic excitation plays a major role in the spectroscopy and photophysics. In a recent paper [J. Phys. Chem. B 2006, 110, 18844], we developed a multidimensional exciton model of electron−torsion coupling that accounts for a number of unusual features in the spectroscopy of poly(phenyleneethynylene). This paper reduces that multidimensional exciton model to a one-dimensional configuration-coordinate (CC) model to facilitate interpretation of the spectroscopy and to allow extension to more complex systems. Because the CC model is derived from a more exact multidimensional model, the approximations inherent in the CC model can be examined quantitatively. The CC model accurately accounts for the line shapes in absorption and emission and the evolution of those shapes with oligomer length. Both fully anharmonic torsional potentials and nonlinear coupling are needed to predict these properties. In addition, the entropic contributions in ...

Theory of optical spectra of impurity centres in crystals: general consideration of quadratic vibronic coupling

A method is proposed for the calculation of the spectra of the multiphonon transitions caused by the quadratic vibronic coupling with a phonon continuum. In the method, the time evolution of the final state is described by the path integrals. By applying the Stratonovich–Hubbard identity, the quadratic coupling is presented as the fluctuating linear coupling; the latter is calculated by the Lax method. As a result, the problem is reduced to the calculation of the determinants of matrices, the elements of which are given by the pair correlation functions of the contributing configurational coordinates. The method has been verified for the case of two mixed modes. Numerical calculations have also been made for a modified Debye model.

Characterization and luminescence properties of Sr2Si5N8:Eu2+ phosphor for white light-emitting-diode illumination

Eu 2 + -doped ternary nitride phosphor, Sr2Si5N8:Eu2+, was prepared by the carbothermal reduction and nitridation method. The Rietveld refinement analysis showed that the single phase products were obtained. Two main absorption bands were observed on the diffuse reflection spectra peaking at about 330 and 420nm, so that the resultant phosphor can be effectively excited by InGaN light-emitting diodes. The emission peak position of (Sr1−xEux)2Si5N8:Eu2+ series varied from 618to690nm with increasing Eu2+ ion concentration. The redshift behavior of the emission band was discussed on the basis of the configuration coordination model.

Optical transition in an impurity centre of a crystal: Mixing of phonons

The new method of calculation of the Fourier transform of the optical spectrum of an impurity centre in a crystal in the case of quadratic vibronic coupling with phonons is proposed. In the method, by applying the Stratonovich identity, the quadratic coupling is replaced by the fluctuating linear coupling; the latter is treated by means of the Bloch–DeDominicis theorem. As a result, the problem is reduced to the calculation of the determinant of the symmetric complex matrix and of the corresponding reciprocal matrix. The matrix elements are given by the pair correlation functions of the contributing configurational coordinates.

Both Spacer Length and Parity Influence the Thermal and Light‐Induced Properties of Iron(II) α,ω‐Bis(tetrazole‐1‐yl)alkane Coordination Polymers

A new series of [mu-tris-{1,n-bis(tetrazol-1-yl)alkane-N4,N4'}iron(II)] bis(perchlorate) spin-crossover coordination polymers ([Fe(nditz)3](ClO4)2]; n = 4-9) has been synthesised and characterised. The ditetrazole bridging ligands provide octahedral symmetry at the iron(II) centres while allowing the distance between iron(II) centres to be varied. These polymers have therefore been investigated to determine the effects of spacer length on their thermal and light-induced spin-transition behaviour. An increase in the number of carbon atoms in the spacer (n) raises the thermal spin-crossover temperature, while decreasing the stability of the light-induced metastable state generated through the light-induced excited spin state trapping (LIESST) effect by irradiating the sample at 530 nm. Remarkably, however, the parity of the spacer also has an effect, enabling the series of complexes to be divided into two sub-series depending on whether the bridging ligand possesses an even or an odd number of carbon atoms. An explanation at the molecular level using the single configurational coordinate (SCC) model is presented.

Influence of multi-step topography on barotropic waves and consequences for numerical modeling

Propagation of barotropic topographic Rossby waves (TRWs) and Kelvin type waves over topography consisting of multiple steps is investigated. The transformation of the wave solution from one limiting case with narrow and small steps most closely approximating a continuous slope to another limiting case with wide and high steps is analyzed. The analysis is based on the numerical simulation of the topographic waves by employing a model with σ-level (terrain following) vertical coordinates and several Z-level (geopotential following) vertical coordinate model configurations with a varying number of vertical levels. An analytical solution for frequencies of quasi-geostrophic waves over a multi-step topography is derived to examine how the wave solution transforms for different vertical resolution (yielding different step sizes). Analysis of the model and analytical results suggests criteria for the vertical resolution of a Z-level model with a given topography to support TRW-like solutions and to prevent the formation of artificial edge-trapped waves. When the model has a coarse vertical resolution yielding wide steps compared to the trapping scale of the wave the quasi-geostrophic waves convert to double Kelvin waves trapped along the step edges. In the model with fine vertical resolution there is a transition from the quasi-geostrophic wave to the TRW solution.

A hybrid coordinate ocean model for shelf sea simulation

The general circulation in the North Sea and Skagerrak is simulated using the hybrid coordinate ocean model (HYCOM). Although HYCOM was originally developed for simulations of the open ocean, it has a design which should make it applicable also for coastal and shallow shelf seas. Thus, the objective of this study has been to examine the skills of the present version of HYCOM in a coastal shelf application, and to identify the areas where HYCOM needs to be further developed. To demonstrate the capability of the vertical coordinate in HYCOM, three experiments with different configurations of the vertical coordinate were carried out. In general, the results from these experiments compares quite well with in situ and satellite data, and the water masses and the general circulation in the North Sea and Skagerrak is reproduced in the simulations. Differences between the three experiments are small compared to other errors, which are related to a combined effect of model setup and properties of the vertical mixing scheme. Hence, it is difficult to quantify which vertical coordinate configuration works best for the coastal region. It is concluded that HYCOM can be used for simulations of coastal and shelf seas, and further suggestions for improving the model results are given. Since HYCOM also works well in open ocean and basin scale simulations, it may allow for a realistic modelling of the transition region between the open ocean and coastal shelf seas.

A crossbeam co-ordinate caliper for the morphometric analysis of lithic nuclei: a description, test and empirical examples of application

Over the last four decades, there has been surprisingly little advance in the quantitative morphometric analysis of Palaeolithic stone tools, especially compared to that which has taken place in biological morphometrics over a comparable time frame. In Palaeolithic archaeology's sister discipline of palaeoanthropology, detailed quantitative morphometric, geometric morphometric, and even 3D geometric morphometric analyses are now seen almost as routine. This period of relative methodological stasis may have been influenced by the lack of homologous landmarks on many lithic tools (essential for any comparative analysis), especially core-based technologies of the Lower Palaeolithic. Archaeological field conditions may also prohibit the use of expensive and delicate precision instruments in certain cases. Here we present a crossbeam co-ordinate caliper that – crucially – both geometrically locates and measures distances between morphologically homologous landmarks upon lithic nuclei via a single protocol. Intra- and inter-observer error tests provide evidence that error levels associated with the instrument fall within acceptable ranges. In addition, we present empirical examples of application in the form of a multivariate analysis of 55 discrete morphometric variables, and a 3D geometric morphometric analysis of co-ordinate landmark configurations derived from Pleistocene lithic nuclei (i.e. ‘cores’ sensu lato). We also introduce to lithic studies some techniques for the study of shape variation that have previously been used with success in biological morphometric analyses. We conclude that use of an instrument such as the crossbeam co-ordinate caliper may provide a useful adjunct to traditional techniques of lithic analysis, particularly in developing a quantitative morphometric approach.

Synthesis and spectroscopic study of copper(II) and manganese(II) complexes with pipemidic acid

The interaction of copper(II) and manganese(II) with pipemidic acid, Hpipem, afforded the complexes [Cu(pipem) 2(H 2O)]·2H 2O, 1 and [Mn(pipem) 2(H 2O)], 2. The new complexes have been characterised by elemental analyses, infrared, UV–vis and X-band EPR spectroscopy in the temperature range from 4 to 300 K. The monoanion, pipem, exhibits O,O ligation through the carbonyl and carboxylato oxygen atoms. Five coordinate square-pyramid configuration has been proposed for 1 and 2, and the fifth apical position is occupied by a coordinated water molecule.

SnO 2/TiO 2 mixed oxide particles synthesized in doped premixed H 2/O 2/Ar flames

SnO 2/TiO 2 mixed oxides with primary particle size ranging between 5 nm ⩽ d p ⩽ 12 nm were synthesized by doping a H 2/O 2/Ar flame with Sn(CH 3) 4 and Ti(OC 3H 7) 4 co-currently. The effects of “flow coordinate,” concentration and flame configurations were investigated with respect to particle size and morphology of the generated mixed oxides. In situ characterization of the mixed oxides was performed using the particle mass spectrometer (PMS), while XRD, TEM, BET and UV–Vis were performed ex situ. Results obtained showed that primary particle size of mixed oxides can be controlled by varying experimental parameters. The mixed oxides have interesting properties compared to those of the pure oxides of TiO 2 and SnO 2, which were also synthesized in flames earlier. Band gap tuning opportunities are possible using mixed oxides.

Influence of physical ageing on the excessive heat capacity of hyperquenched silicate glass fibers

Two types of hyperquenched continuous glass fibers, basaltic glass fibers and soda-lime silicate glass fibers, are thermally aged within a temperature range from 0.55Tg to 0.95Tg, where Tg is the glass transition temperature. The results show the complexity of enthalpy relaxation of the aged fibers. During up-scanning of the aged fibers in a differential scanning calorimeter, a relaxation exotherm occurs above a certain temperature, which is due to the release of the excess energy relative to that of a glass cooled at the rate 0.33K/s. At a certain ageing temperature, an endotherm occurs prior to the appearance of the exotherm. There is a smooth crossover between the endotherm and the exotherm. The gradual shift of the crossover from lower to higher temperature with increasing ageing temperature is not due to the distribution of fictive temperatures, but to a distribution of the excess potential energy over all configurational coordinates. A phenomenological equation has been proposed to describe the decrease of the remaining energy with increasing ageing temperature.

Incremental Theory of Diffraction: A New-Improved Formulation

In this paper, a general systematic procedure is presented for defining incremental field contributions. They may provide effective tools to describe a wide class of scattering and diffraction phenomena at any aspect, within a unitary, self-consistent framework. This procedure is based on a generalization of the incremental theory of diffraction (ITD) localization process for uniform cylindrical, local canonical problems with elementary source illumination and arbitrary observation aspects. In particular, it is shown that the spectral integral formulation of the exact solution for the local canonical problem may also be represented as a spatial integral convolution along the longitudinal coordinates of the cylindrical configuration. Its integrand is then directly used to define the relevant incremental field contribution. For the sake of convenience, but without loss of generality, this procedure is illustrated for the case of local wedge configurations. Also, a specific suitable asymptotic analysis is developed to derive new closed form high-frequency expressions from the spectral integral formulation. These expressions for the incremental field contributions explicitly satisfy reciprocity and are applicable at any incidence and observation aspect. This generalization of the ITD localization process together with its more accurate asymptotic analysis provides a definite improvement of the method.

GENERALIZED EULERIAN COORDINATES FOR RELATIVISTIC FLUIDS: HAMILTONIAN REST-FRAME INSTANT FORM, RELATIVE VARIABLES, ROTATIONAL KINEMATICS

We study the rest-frame instant form of a new formulation of relativistic perfect fluids in terms of new generalized Eulerian configuration coordinates. After the separation of the relativistic center of mass from the relative variables on the Wigner hyper-planes, we define orientational and shape variables for the fluid, viewed as a relativistic extended deformable body, by introducing dynamical body frames. Finally we define Dixon's multipoles for the fluid.

Electron beam and gamma irradiation effects on amorphous chalcogenide SbSe 2.5 films

In this article, the effects of the electron-beam and gamma irradiation on the features of chalcogenide SbSe 2.5 films have been studied. The films showed an amorphous to partially crystalline phase at doses ranging from 3 to 12 kGy. Optical absorption measurements have been performed where the results reflected a great dependence of the fundamental absorption edge on the irradiation dose. The radiation induced allowed indirect transition with a decrease in the energy gap as the dose increased. The decrease in the gap was a little higher for electron than that for gamma irradiation. This behavior is believed to be associated with the generation of excess of electronic localized states. The change in the optical gap may be explained in terms of diminution of disorder, defects in the structural bonding and crystal field mechanism. Moreover, the characteristic features of the irradiated films have been studied using scanning electron microscope. SEM observation showed a grain growth on the film surface through which the surface morphology has been demonstrated. Accordingly, a structural model concerning the configurational coordinate has been proposed, based on the assuming tri-coordinated Sb atoms and di-coordinated Se atoms, that confirmed the information obtained from the scanning electron microscope. So, Sb–Se bonds in pyramidal form of molecules with excess of Se rings have been formed as a result of irradiation process.

North Atlantic Simulations with the Hybrid Coordinate Ocean Model (HYCOM): Impact of the Vertical Coordinate Choice, Reference Pressure, and Thermobaricity

The viability of a generalized (Hybrid) Coordinate Ocean Model (HYCOM), together with the importance of thermobaricity and the choice of reference pressure, is demonstrated by analyzing simulations carried out using the World Ocean Circulation Experiment (WOCE) Community Modeling Experiment (CME) Atlantic basin configuration. The standard hybrid vertical coordinate configuration is designed to remain isopycnic throughout as much of the water column as possible while smoothly making a transition to level (pressure) coordinates in regions with weak vertical density gradients, such as the surface mixed layer, and to terrain-following coordinates in shallow-water regions. Single-coordinate (pressure or density) experiments illustrate the flexibility of the model but also bring forward some of the limitations associated with such a choice. Hybrid experiments with potential density referenced to the surface ( su) and to 20 MPa (;2000 m) (s 2) illustrate the increased influence of pressure errors with increasing distance from the reference pressure. The su hybrid experiment does not properly reproduce the northward flow of Antarctic Bottom Water (AABW), and large errors in near-surface pressure gradients in the s 2 experiment produce a wind-driven gyre circulation that is too strong, when compared with observations, and a North Atlantic Current that follows an unrealistic path. These near-surface and nearbottom pressure errors are removed when thermobaric effects are included, resulting in a more accurate representation of the upper-ocean gyre circulation, the northward AABW flow near the bottom, and the meridional overturning circulation and heat flux.

Generalized electronic diabatic scheme: Diagonalizing the electronic Hamiltonian for artificial molecular systems. How do molecular meccanos move?

AbstractA quantum–classic model is presented and used to describe systems ranging from normal molecules up to electronic systems sensed in real space. The quantum system is a set of n‐electrons; a positive background in real space completes the model. A generalized electronic diabatic (GED) theory is introduced. The diabatic functions diagonalize the electronic Hamiltonian for any arrangement of the positive background. Physical quantum states are represented as linear superpositions in the diabatic basis; this latter is always fixed. For systems sensed in real space, the coefficients of the linear superposition are functions of the real space configuration coordinates. Physical changes are produced by interactions with external sources/sinks of energy. An interaction couples different diabatic states; diagonalizing the electronic Hamiltonian plus the couplings leads to new coefficients describing physical states. Among other things, these couplings can be used to simulate the effects produced by scanning tunneling microscopy, atomic force, and transmission electron microscopy on substrates located in real space. The important thing is that time–evolution in electronic Hilbert space can be related to actual motion in real space. The experiment of lateral hopping of a substrate on a metallic surface induced by vibration excitation and followed with scanning tunneling microscope is discussed. A result of the present work is that motion of molecular meccanos reflects then time–evolution in electronic Hilbert space. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004

An intrinsic observer for a class of lagrangian systems

We propose a new design method of asymptotic observers for a class of nonlinear mechanical systems: Lagrangian systems with configuration (position) measurements. Our main contribution is to introduce a state (position and velocity) observer that is invariant under any changes of the configuration coordinates. The observer dynamics equations, as the Euler-Lagrange equations, are intrinsic. The design method uses the Riemannian structure defined by the kinetic energy on the configuration manifold. The local convergence is proved by showing that the Jacobian of the observer dynamics is negative definite (contraction) for a particular metric defined on the state-space, a metric derived from the kinetic energy and the observer gains. From a practical point of view, such intrinsic observers can be approximated, when the estimated configuration is close to the true one, by an explicit set of differential equations involving the Riemannian curvature tensor. These equations can be automatically generated via symbolic differentiations of the metric and potential up to order two. Numerical simulations for the ball and beam system, an example where the scalar curvature is always negative, show the effectiveness of such approximation when the measured positions are noisy or include high frequency neglected dynamics.

Knowledge of Variable Binding in VP–Ellipsis: Language Acquisition Research and Theory Converge

In this paper, we relate results from recent experimental study of young children's (3;0–7;11) comprehension of coordinate VP–ellipsis structures in English to a new theoretical proposal regarding their representation. Historically, theoretical treatments of these structures have been challenged by the nature of the ambiguity they involve, which includes both a “sloppy” interpretation (represented in terms of a bound variable) and a “strict” interpretation (represented as referential), at the same time that other interpretations are ruled out. Based on our study of language acquisition, we propose a solution capturing the ambiguity in the syntax, including two different types of operator–variable binding (local and long–distance) over a shared coordinate configuration. Pragmatic focus motivates the choice of the syntactic option for the long–distance strict interpretation. Empirical results reveal that, at all ages, (i) the sloppy interpretation is preferred, (ii) the strict interpretation is nevertheless in evidence, (iii) ungrammatical interpretations are ruled out, and (iv) choice of the strict reading is influenced by semantic/pragmatic factors.