Analytical upper bounds for convolutional coded CPM over rings

Analytical upper bounds on symbol error probability for ring convolutional coded Continuous Phase Modulation (CPM) with Maximum Likelihood Sequence Detection (MLSD) are presented. The constructed bounds for the investigated systems are shown to be asymptotically tight for increasing channel Signal-to-Noise Ratio (SNR) values. This work provides an analysis tool for the investigated systems. The analysis method is very general. It may be applied to any trellis based coding schemes.     

Synthesis of starch benzoate in aqueous media

Summary The results of investigating starch benzoate (SB) synthesis in aqueous media are presented in this study. Starch esterification with benzoyl chloride was performed in two steps, the first step being the alkalization of starch and the second step esterification. The influence of the concentration of reactants, reaction medium composition, temperature and time of synthesis on the degree of substitution (DS), degree of swelling in water and thermal stability of the synthesized starch benzoate was investigated. The optimal conditions for the synthesis of starch benzoate with degree of substitution from 0.23 to 1.76 were determined. It was shown that starch benzoate with a DS of 1.76 practically did not swell in water. However, starch benzoate is less thermally stable than native starch probably due to a change in the supermolecular order induced by the esterification reaction. Received: 18 March 2002/Revised version: 18 October 2002/ Accepted: 28 October 2002 Correspondence to Katarina Jeremić     

Piezoresistivity and electro-thermomechanical degradation of a conducting layer of nanoparticles integrated at the liquid crystal elastomer surface

When a liquid crystal elastomer (LCE) is reprocessed with conducting nanosized particles a conducting layer can be formed at the LCE surfaces. Here, two different LCE materials and two different conducting carbon particles were used. These four reprocessed LCEs were investigated when subject to a thermal phase transition and mechanical extension. Here it is shown that the resistance change with strain ('piezoresistivity') for these reprocessed LCEs can be described through lattice percolation and geometrical changes in the LCE shape. The mechanisms and rate of degradation are also described for the conducting layer as a function of the number of electro-thermomechanical strain cycles performed.     

Failure analysis of the combat jet aircraft rudder shaft

This paper analyzes failure causes of the combat jet aircraft rudder shaft (RS) which occurred during the flight mission. A finite element method (FEM), utilized to determine the stress state of the RS subjected to hinge moment ultimate load, resulted in the high stress concentration sites around the rivet holes. The longitudinal crack was initiated from the corrosion pit in the zone of the rivet hole, where the fatigue beach marks were observed. The inner surface of the RS was heavily corroded. Moreover, pitting corrosion has destroyed approximately 50% of the wall thickness. Based on the presented results it was concluded that the failure of the RS had a character of fatigue combined with heavy corrosion. Therefore, it is recommended that the RS should be redesigned; the material changed into more corrosion resistant one and the maintenance procedure changed in order to avoid future similar failures.     

Spectral determination of graphs whose components are paths and cycles

We consider the class of graphs each of whose components is either a path or a cycle. We classify the graphs from the class considered into those which are determined and those which are not determined by the adjacency spectrum. In addition, we compare the result with the corresponding results for the Laplacian and the signless Laplacian spectra. It turns out that the signless Laplacian spectrum performs the best, confirming some expectations from the literature.     

Effects of liquid burn rate catalysts on Rheological Properties of High-Energy Composite Propellants

Effects of several liquid burning rate catalysts on rheological properties of composite rocket propellants on the basis of hydroxy-terminated polybutadiene as a binder and ammonium perchlorate as an oxidizer have been examined. Theoretical explanation of the observed effects of liquid catalysts on certain rheological properties of the mentioned propellants are given. Laboratory procedures for synthesis of used catalysts are described. The results of physico-chemical characterization of synthesized catalyst are also presented.     

Power allocation and code construction for space-time turbo trellis codes with partial CSI feedback

Conventional space-time turbo trellis coding (STTuTC) schemes allocate transmit power equally to the available antennas. This is not optimal if channel state information (CSI) is available at the transmitter. A STTuTC scheme is considered with partial CSI knowledge that optimally allocates power to the transmit antennas. This scheme is referred to as STTuTC with dynamic transmit power allocation (STTuTC/DTPA). The optimum four-state constituent code and power allocation are presented. Simulation results show that the STTuTC/DTPA scheme with the new code outperforms conventional STTuTC schemes.