Vol. 35 No. 1 (2003)

In this paper is considered a direct estimation technique of model parameters of components (subsystems) of a feedback system using an extended least squares algorithm. There are three components of system may be estimated, feedback, feedforward, and noise. It has been assumed that the system considered was linear and time invariant. A common estimation technique for closed loop system is indirect, and under assumption that only one component will be estimated while the other components in the closed loop are known. The analysis shows that the proposed technique is unnbias. In the proposed…

Anaerobic hybrid bioreactor is a combination of suspended and attached growth systems. Stone was used as the microorganism attachment media. The feeding solution was made from molasses diluted to COD concentration of 10,000, 20,000, 30,000 and 40,000 mg/L. The hydraulic detention time was 30 hours and the height ratio between suspended and attached growth system was 0.5. The result shows that the organic concentration seems to be on of the determining factors. Furthermore, since the methane production was still low enough, it seems that the process has not achieved its optimum condition for…

Computer model is developed to relate parameters that determine the performance of a contact-stabilization system. Based on mass and substrate balance in the system, relationships between the variables are developed, then simulations using various values of the parameters can produce trend lines indicating the behavior of a system as well as the required conditions to reach an expected performance. When the operating conditions, such as recycled sludge and wasted sludge are changed, the model demonstrates alterations of the performance consistent to the developed mathematical relationships.…

Previous numerical and experimental investigations found that some envelopes of bichromatics surface water waves show deformation during their propagation along the wave tank in Hydrodinamic Laboratory. In this paper we present investigation on the maximum amplitudes of bichromatics envelopes at every position along the tank, to observe the amplification factor of a signal deformation. As we consider a signaling problem, a spatial Nonlinear Schrodinger (sp-NLS) model is used here. The profiles of waves envelope as a function of time and space are computed numerically from this model.…

A graph G is called hamiltonian if it contains a Hamilton cycle, i.e. a cycle containing all vertices. Deciding whether a given graph has a Hamilton cycle is an NP-complete problem. But, it is a polynomial problem within some special graph classes. In this paper we consider three classes of grid graphs, namely rectangular grid graph, eta grid graph and omega grid graph. Our main result characterizes which of these graphs are hamiltonian.

Composite of zinc oxide (ZnO) nanoparticles in polyethylene glycol (PEG) has been produced by mixing the as prepared ZnO colloid with a solution of PEG in ethanol. ZnO colloid was produced by hydrolizing zinc acetate in ethanol solution. The produced composite exhibits a wide band excitation spectra compared to ZnO colloid to allow the excitation using a wide range excitation wavelength for producing high green luminescence intensity. Since ZnO nanoparticles were trapped in a matrix of polymer (solid phase) no further growing as well as agglomeration process took place (as observed in ZnO…