Open Access

Echinoderm skeletons are described within a hierarchical framework ranging from complete organisms to the ultrastructural level. They consist of numerous elements which can be isolated, connected by soft tissue or locked together in rigid structures. The top level considers skeletons as a whole with all associated elements and the basic symmetry of the echinoderms. The next level deals with the structural analysis and modeling of echinoids with respect to the growth parameters and stress resistance of the corona. The flexibility and movement has also been studied for the stalks and arms of recent and fossil crinoids. The next level deals with the elaborate morphology and types of symmetry found in single skeletal elements. The numerous types of stereom architectures found within the elements of all echinoderms are highly correlated to specific functions. A high number of recent studies concern the last hierarchical level on ultrastructure and biomineralization. Lightweight aspects of the skeleton are especially present at the level of conjoined plates, single elements and the stereom.

The paper presents the design of a baseband pi/4-DQPSK complex wavelet packet modulation CWPM transceiver and the results of its FPGA implementation. The design uses 8-point Discrete Wavelet Packet Transform (DWPT) and its inverse as core processing modules. All modules have been designed using VHDL programming language together with the Altera software tools Quartus II 9.1 and ModelSim 6.5b. The transceiver was implemented on a Cyclone III board.

When an abrupt parametric fault occurs in a system, active fault tolerant control (FTC) aims at reconstructing the system input after the fault has been isolated and estimated so that the fault is compensated and the system output follows a desired trajectory despite the fault.