Solids

Intrinsic evolution in evolvable hardware research has hitherto been limited to using standard electronic components as the media for problem solving. However, recently it has been argued that because such components are human designed and intentionally has predictable responses; they may not be the optimal medium to use when trying to get a naturally inspired search technique to solve a problem. Evolution has been demonstrated as capable of exploiting the physical properties of material to form solutions; however, by giving evolution only conventional components, we may be placing arbitrary constraints on our ability to solve certain problems. We have shown for the first time, that liquid crystal can be used as the physical substrate for evolution. We demonstrate that it is possible to evolve various functions, including a tone discriminator, in materio.

The micromechanisms of deformation and fracture in tension were analyzed in a commercial polypropylene nonwoven geotextile material in a wide range of strain rates. Two different loading scenarios (smooth and notched specimens) were considered to study how these mechanisms are modified in presence of a stress concentration. The nonwoven fabric presented significant deformability and energy-absorption capability, which decreased with the strain rate, together with a high level of strength, which increased with strain rate. In addition, the material was notch-insensitive as the stress concentration around the crack tip was relieved by marked nonlinear behavior, which induced crack blunting. Different experimental techniques (standard mechanical tests, in situ testing within the scanning electron microscope, digital image correlation, etc.) were used to establish the sequence of deformation and failure processes and to link these micromechanisms with the macroscopic behavior.

This paper is concerned with the systems aspects of the Solid Free- form Fabrication (SFF) technology, i.e., the issues that deal with getting an external geometric CAD model to automatically control the physical layering fabrication process as directly as possible, regardless of the source of the model. The general systems issues are described, the state of systems research is given, and open research questions are posed.

Distance relay is the main protection of power transmission lines and make an important role in power system stabilization if it operates selective and instantaneous. In this paper, the trajectory of the fault impedance is determined. It is shown that in the end of the first zone or in the middle of the second zone, distance relay could not make a correct decision for operating if the fault occurs with arc. So to overcome this problem, in this paper a novel technique using total harmonic distortion (THD) is proposed. The proposed method makes the distance relay more selective and instantaneous.