[en] Two-body systems of predictive mechanics are compared with single particle systems in a potential. Study of the limit where one of the bodies is fixed

[en] This paper presents a new principle and method of kinematics to analyze the singularity of Stewart-Gough parallel manipulators and addresses the property identification of the position-singularity loci of the 6-3 Stewart-Gough manipulators for special orientations. Based on the kinematic relationship of a rigid body, a necessary and sufficient condition that three velocities of three non-collinear points in a moving rigid body can determine a screw motion is addressed and some typical singular configurations of the 6-3 Stewart-Gough parallel manipulators are also addressed in detail. With the above-mentioned condition, a symbolic analytical polynomial expression of degree three in the moving platform position parameters, representing the position-singularity locus of the 6-3 Stewart-Gough manipulators for special orientations, is derived: and the property identification of the position-singularity loci of the 6-3 Stewart-Gough manipulator for these special orientations is investigated at length. It is shown that position-singularity loci of the 6-3 Stewart-Gough parallel manipulator for these special orientations will be a plane and a hyperbolic paraboloid, even three intersecting planes

[en] This paper presents the dynamic analysis and kinematic parameter optimization of a coupled linkage system for the purpose of employing the system in construction industry. So far, the kinematic optimization of wheel loaders was approached heuristically rather than utilizing elaborate theoretical examinations due to the complexity of coupled linkage structures. The results of the theoretical analysis and kinematic parameter optimization are presented in this paper. A wheel loader with Z-bar linkage was analyzed. For a given end-effector path, the linkage system was optimized to carry out effective motion while exhibiting minimum power consumption during operation. A modified principle of reduced system was applied in order to execute the dynamics analysis of the coupled linkage system. As a result, an optimal Z-bar linkage structure and a distribution of power consumption within the given conditions were obtained

[en] The author gives a presentation of special relativistic kinematics in a form which is suitable for epistemological discussion. This presentation entails four steps: a mathematical system, a physical system, an empirical interpretation and a particular experiment. At the end of third step a definition of The Theory of Special Einsteinian Kinematics is proposed. (Auth.)

[en] For spherical mechanisms, instantaneous poles are as the counterparts of instant centers in planar mechanisms. However, they are not fully exploited to study the kinematic behavior of spherical mechanisms as the instant centers are for planar ones. The main purpose of this paper is the singularity analysis of multi-degree-of-freedom (DOF) spherical mechanisms. After reviewing the concepts of spherical motion and instantaneous poles, a geometrical technique is presented to identify the singularities of the mechanisms using the properties of instantaneous poles. The method is fast and comprehensive that can be easily employed for all types of multi-DOF spherical mechanisms. Two illustrative examples are included to show the effectiveness of the presented method and the obtained singularities are verified analytically

[en] Within the framework of traditional cosmography (without reference to Friedmann's cosmological equations) the metric of Robertson-Walker type is found, for which a relationship between conformal and cosmic times coincides in form with the transformation of light cone generating lines with respect to a group of special conformal transformations. The metric gives birth to a constant value of the deceleration parameter equal to minus one second, which reproduces the effect of accelerating expansion of the Universe in good agreement with observations. (authors)

[en] This book tells of hydromechanics, which is about basic properties of hydromechanics such as conception, definition, mass, power and weight, and perfect fluid and perfect gas, hydrostatics with summary, basic equation of hydrostatics, relative balance of hydrostatics, and kinematics of hydromechanics, description method of floating, hydromechanics about basic knowledge, equation of moment, energy equation and application of Bernoulli equation, application of momentum theory, inviscid flow and fluid measuring.

[en] In this work, effects of rotation on the evolution of kinematic and thermal fields in homogeneous sheared turbulence are investigated using second order closure modeling. The Launder-Reece-Ro di models, the Speziale-Sarkar-Gatski model and the Shih-Lumley models are retained for pressure-strain correlation and pressure-temperature correlation. Whereas classic models are retained for time evolution equations of kinematic and thermal dissipation rates. The fourth order Runge-Kutta method is used to resolve three non linear differential systems obtained after modeling. The numerical integration is carried out separately for several values of the dimensionless rotation number R equal to 0, 0.25 and 0.5. The obtained results are compared to the recent results of Direct Numerical Simulations of G.Brethouwer. The results have confirmed the asymptotic equilibrium behaviors of kinematic and thermal dimensionless parameters. Furthermore they have shown that rotation affects not only kinematic field but also thermal field. The coupling between the Speziale-Sarkar-Gatski model and the Launder-Reece-Rodi model is of a big contribution on the prediction of kinematic and thermal fields

[en] We show that to a very good approximation there exists in general an equivalence between intermittency and the assumption that the first factorial correlator F₁₁ is independent of bin size. We further show that strict bin size independence imposes for the possible values of the intermittency index φ, φ=0 or φ=1. (orig.). With 2 figs

[en] The investigation of positronium (Ps) promoted the development of QED and the formalism of the relativistic bound state in quantum field theory. The typical feature of the modern stage of these investigations is the superior precision of absolute measurements of the orthopositronium (^TPs) lifetime and of the corresponding calculations. They allow us to state with confidence that the experimental rate λ_T of ^TPs self-annihilation (3γ-annihilation) exceeds the theoretical value λ_T(theor) = 7.03830 ± 0.0005 μs^-1 (∼ 0.0007%). The annihilation of free ^TPs into one real photon is kinematically forbidden in standard QED. A way out of this impasse can be found using the hypothesis of mixing of ^TPs with a 'twin' ^TPs' in the 'mirror Universe' (the coupling constant satisfies the condition 10^-6 < ε < 10^-3) because ^TPs, unlike parapositronium ^SPs, emits and absorbs one virtual photon. This fact can be used to construct a consistent kinematics of one-photon ^TPs annihilation based on the assumption that the 'mirror Universe' carries away the recoil energy and momentum. The purpose of this work is to refine the earlier formulation of the phenomenology of one-photon ^TPs annihilation. On this basis, the authors substantiate the necessity to supplement modern experimental investigations (carried out since 1989) with a program of critical experiments in which special emphasis is placed on the search for one-photon annihilation