Dual properties of spacetime under an alternative Lorentz transformation

In flat spacetime, the fourth space coordinate in special relativity (SR) is equivalent to the coordinate time t_E. We will show, however, that this definition of physical time is not unique. Another natural choice of coordinate time, t_A, with absolute synchronization is allowed. Spacetime would exhibit dual properties, namely relativistic and absolute. In an arbitrary inertial frame, the relationship of the above two kinds of coordinate time corresponds to a resynchronization, and the Lorentz transformations can be written in an alternative form, which is called the generalized Galilean transformation (GGT). Although the absolute property is still hidden in nearly all types of experiments, the advantages of the above approach are as follows: (1) It will give us a deeper understanding of SR, including the basis of length contraction, time dilation and the interaction between moving objects and the physical vacuum. (2) It will provide a wider research domain than SR; for example, superluminal motion is predicted and has obtained growing experimental support.     

Random phase-coded multiplexing of hologram volumes using ground glass

We apply an encoding method, random phase-coded multiplexing, to volume hologram multiplexing and demonstrate the recording of 100 holograms in LiNbO₃: 0.01% Fe. A theory is developed to interpret the noise generated by this method, and a computer simulation is provided for direct comparison.     

Image formation for two-dimensional periodic object using Talbot effect

The conditions under which the information inside each subcell of a two-dimensional (2D) object, periodic in orthogonal directions, is replicated throughout all the subcells of the unit cell are obtained. Relative-phase relationship among all the subcells depends only on the number of subdivision but not the length-to-width ratio of the unit cell. From this relationship, the wave amplitude at all the subcells is calculated by superposition of the information from all the subcells in the orginal object. A 2D object periodic in nonorthogonal directions can be decomposed as a set of laterally shifted 2D objects which are periodic in orthogonal directions. Hence, the image formation problem for nonorthogonally periodic object can be solved directly from the superposition of results for the laterally shifted, orthogonally periodic ones.     

Stability conditions for a pipeline polling scheme in satellite communications

This paper considers the unknown stability conditions of a pipeline polling scheme proposed for satellite communications. This scheme is modelled as a cyclic-service system with limited service and reservation. The walk times and the maximum number of services to be performed during each polling are dependent on the queue lengths of the stations. The main result is the derivation of the necessary and sufficient stability conditions of the system. Our approach is to map the multi-dimensional stability problem into many 1-dimensional stability problems through the concept of the least stable queue. The least stable queue is one that will become unstablefirst when the system load increases in some parameter region. The stability of the least stable queue thus implies stability of the system. The stability region for the whole system is then the union of the queue stability regions of all the least stable queues that are obtained through dominant systems and Loynes' theorem. We also propose a computable sufficient condition that is tighter than the existing result and present some numerical results.     

Experimental observation of a striking similarity between quantum hall transport coefficients

The derivative of the Quantum Hall resistance, ρ_xy, with respect to the carrier density, n, has been measured for a two-dimensional electron gas in a GaAs-Al_xGa_1?xAs heterostructure, as a function of magnetic field. dρ_xy/dn exhibits a remarkable similarity to the diagonal resistivity, ρ_xy, to the extent that one is almost directly proportional to the other. Our result suggests the possibility of a fundamental connection between the two quantities.     

Acousto-optic diffraction at liquid-solid interface with light incident at critical angle

A new acousto-optic diffraction configuration is described. At a liquid-solid interface, a light beam is incident from the solid side of higher refractive index. The maximum acousto-optic diffraction of the Raman-Nath type occurs in the liquid with light incident at the critical angle. The angular dependence of the diffraction efficiency indicates accurate optical alignment requirement. Application to acoustic imaging is briefly discussed.     

Optimal controller placement in modal control of complex systems

Within the framework of modal control of large systems, a simple approach is advanced for the determination of optimal control configuration under an energy constraint, i.e., optimal locations of a limited number of controllers such that the total energy requirement for control is minimized. It is shown that the resulting design criterion is a simple function of projections of the control matrix onto components of eigenvectors associated with the affected eigenvalues. Furthermore, it is applicable to both single-input and multi-input systems. Systems possessing distinct complex eigenvalues are considered but the approach is equally applicable to other types of systems. Examples show that the minimum-energy control configuration also tends to be the most effective in terms of accomplishing control objectives.