This paper presents a satellite navigation method which is based on the synchronization of user clock using bi-directional satellite communication. This method is effectively applied to cope with the reduction of range-finding data due to satellite failure or limited field in view, and also applicable for Radio Determination Satellite System (RDSS) like GEOSTAR which applies two geostationary satellites as means of relaying range-finding signals and supplies communication service at the same time. Analytical results are also discussed relating to this subject.
Membrane wings, such as sails of yachts and hanggliders, have quite complicated aerodynamic characteristics owing to interactions between compliant wings and the flow around them. All the existing methods of solution for three-dimensional membrane wing theories contain iterative procedures to deal with the strong nonlinearity of the problem. We assumed the uniform tension to weaken this nonlinearity and eliminated the iterative procedures. We applied this method to the problem of circular elastic membrane wings. Numerical results have been compared with experimental results. The consistency between the analysis and the experiment shows the validity of our method. The existence of two equilibria is also confirmed.
This paper considers approximating unsteady aerodynamic forces acting on a rectangular wing in the time domain. Time responses of the aerodynamic forces caused by a step movement of a rectangular wing in incompressible flow are calculated by using the time domain vortex element method. Transient characteristics in the step responses can be represented by one decreasing function regardless of wing motions. By approximating the decreasing function with a set of exponential functions and by calculating apparent mass coefficients and steady state forces, a mathematical model for the aerodynamic forces in the form of 1st-order linear time-invariant differential equations (the state equations) is obtained. The results obtained for the example problems show that a good fit to the aerodynamic forces can be achieved with two exponential functions approximating the decreasing function.
State variable inequality constraints are the last and the hardest problems in optimal control. So far in some methods we have had we cannot solve every problem, in the others we only obtain approximate solutions. In this paper a new formulation (Monotonous subarc method) for solving optimal control problems with state variable inequality constraints are presented, in which we can get accurate solutions of any state-bounded problems with ordinary two-point-boundary algorithms.
This paper presents two boundary techniques which are useful for FEM analysis of composite laminates. One is a rotational symmetric boundary technique and the other is a quasi three-dimensional boundary technique. The use of the rotational symmetric boundary technique allows a smaller FEM model. With the use of the quasi three-dimensional boundary technique, quasi three-dimensional analysis of composite laminates can be performed on the conventional 3-D FEM program. These techniques can readily be adopted to FEM programs.