Search results for "MECHANICS"
showing 10 items of 9361 documents
Summary of Trap Properties
2009
Three-dimensional confinement of charged particles requires a potential energy minimum at some region in space, in order that the corresponding force is directed toward that region in all three dimensions. In general, the dependence of the magnitude of this force on the coordinates can have an arbitrary form; however, it is convenient to have a binding force that is harmonic, since this simplifies the analytical description of the particle motion.
Numerical analysis of masonry structures via interface models
2001
The present paper is devoted to the theoretical formulation and numerical implementation of an interface model suitable to simulate the behavior of mortar joints in masonry structures. The interface laws are formulated in the framework of elasto-plasticity for non-standard materials in order to simulate the softening response which occurs along the decohesion process in presence of shear and tension tractions. A variable material dilatancy parameter is introduced together with a further geometrical dilatancy related to the roughness of contact surfaces after joint fracture. An asperity model is adopted with the aim to describe the evolution of the contact surface shape during the loss of co…
In-beam study of the 128, 130Xe nuclei
1981
Abstract The level structure of 128,130Xe has been studied in the (α, 2nγ) and (3He, 3nγ) reactions on enriched Te targets using in-beam γ-ray spectroscopic methods. For both nuclei the existing information about positive-parity level structure was enriched and many new negative-parity two-quasiparticle states were observed. Isomeric states with the half-lives of 63 ± 12 ns in 128 Xe and 4.8 ± 0.5 ns in 130 Xe were found. For collective positive-parity states the interacting boson model, and calculations based on Bohr hamiltonian were compared with the experimental data.
A fully manipulable damped driven harmonic oscillator using optical levitation
2020
We implement an experimental system based on optical levitation of a silicone oil droplet to demonstrate a damped driven harmonic oscillator. The apparatus allows us to control all the parameters present in the differential equation that theoretically describes such motion. The damping coefficient and driving force can be manipulated in situ by changing the pressure in the apparatus and by applying a variable electric field. We present two different experimental procedures. First, a transition from the overdamped to underdamped regimes is demonstrated by gradually lowering the air pressure. The characteristic resonance associated with an underdamped driven harmonic oscillator is observed by…
High resolution study of the 3ν1 band of SO2
2009
Abstract The second overtone band 3 ν 1 of sulfur dioxide has been studied for the first time with high resolution rotation-vibration spectroscopy. About 3000 transitions involving about 900 upper state energy levels with J max. = 66 and K a max. = 24 have been assigned to the 3 ν 1 band. In the analysis, an effective Hamiltonian taking into account accidental interactions between the vibrational states (3 0 0), (2 2 0), and (0 4 1) was used. The Watson operator in A -reduction and I r representation was used in the diagonal blocks of the Hamiltonian. As the result of analysis a set of parameters reproducing the initial experimental data with the rms = 0.00028 cm −1 was obtained.
On a topological interpretation of electronic and vibrational molecular energies
1998
Abstract A relationship between Randic's connectivity index and various quantum mechanical parameters derived from the Huckel Molecular Orbital (HMO) approach is demonstrated. When applied to conjugated hydrocarbons, this index represents the measure of the global π electron molecular energy and, therefore, of the resonance energy. Moreover, the development of the procedure, allows the introduction of a new definition of the bond order which, in turn, makes possible a better prediction not only for bond lengths of naphtalene but also for the resonance integral and conjugation energy for butadiene. Also, a corrected value for the Randic index is deduced, which allows for the reduction of the…
Analysis of static friction and elastic forces in a nanowire bent on a flat surface: A comparative study
2014
ZnO nanowires bent to a complex shape and held in place by static friction force from supporting flat surface are investigated experimentally and theoretically. The complex shapes are obtained by bending the nanowires inside a scanning electron microscope with a sharp tip attached to a nanopositioner. Several methods previously described in the literature are applied along with author's original method to calculate the distributed friction force and stored elastic energy in the nanowires from the bending profile. This comparative study evidences the importance of the usage of appropriate models for accurate analysis of the nanowires profile. It is demonstrated that incomplete models can lea…
A new method for creating sparse design velocity fields
2006
We present a novel method for the computation of mesh node sensitivities with respect to the boundary node movement. The sensitivity field is sparse in a sense that movement of each boundary node affects only given amount of inner mesh nodes, which can result in considerable savings in the storage space. The method needs minimal control from the user, and it does not place any restrictions (such as block structure) on the mesh. Use of the method is demonstrated with a shape optimization problem using CAD-free parametrization. A solution to the classical die-swell free boundary problem by coupling the boundary node locations with the state variables is also presented. In that case, sparsity …
Developing Online Collaborative Games for e-Learning Environments
2014
Based on our experience, we believe that games, competition and teamwork offer a pleasant and active way of learning. This is much more efficient when the learner has a smile on his face, when he is astonished and curious about next levels and finds the game sufficiently challenging and fun to try again. Our application proposal has the purpose of implementing an e-Learning platform for improving the teaching and learning process in somewhat abstract domains, such as computer architecture or object oriented programming, with the help of games. These games are time-dependent and are able to support collaboration between groups. To this date there are two learning games implemented: a crosswo…
The microscopic theory of diffusion-controlled defect aggregation
1998
Abstract The kinetics of diffusion-controlled aggregation of primary Frenkel defects ( F and H centers) in irradiated CaF 2 crystals is theoretically studied. Microscopic theory is based on the discrete-lattice formalism for the single defect densities (concentrations) and the coupled joint densities of similar and dissimilar defects treated in terms of the Kirkwood superposition approximation. Conditions and dynamics of the efficient F center aggregation during crystal heating after irradiation are analyzed.