Hard polycrystalline eutectic composite prepared by spark plasma sintering

A polycrystalline eutectic B4C–TiB2 composite was prepared by spark plasma sintering. The starting eutectic powder was obtained by mechanical grinding of the directionally solidified eutectic B4C–TiB2 alloy. The microstructure of the polycrystalline composite exhibited randomly oriented eutectic grains with an average size of about 50–100 μm. Eutectic grains consisted of boron carbide matrix reinforced by titanium diboride inclusions. The secondary eutectic structure in the grain boundary is formed at sintering temperature higher than 1700 °C. XRD analysis revealed that the eutectic B4C–TiB2 composite consist mainly of B4C and TiB2 phases. The measured Vickers hardness was in the range of 32.35–54.18 GPa and the average fracture toughness of the samples was as high as 4.81 MPa m1/2. The bending strengths of the composite evaluated at room temperature and at 1600 °C were 230 and 190 MPa, respectively

Morphology and properties of new porous biocomposites based on biogenic hydroxyapatite and synthetic calcium phosphates

The new porous biocomposites have been obtainted using calcium phosphates (SCP-glass) synthesized by chemical precipitation and the biogenic hydroxyapatite (BHA-glass) extracted from animal bones. The composites prepared at the same conditions have a density of about 2.78 g/cm3 (SCP-glass) and 2.92 g/cm₃ (BHA-glass) and show good compression strength of about 127 MPa (SCP-glass) and 98 MPa (BHA-glass). The recrystallization of phosphates in composites due to their liquid phase sintering has been revealed

An exploration of simple reactive responses for conveying aliveness using the Haru robot

This paper describes the development of simple robotic reactive responses for the tabletop robot Haru. While reactive responses in organisms are associated with a biological purpose, they may also play a role in conveying agency in the sense of aliveness. In this paper, we are therefore interested in the design of simple reflexive behaviors that can convey a sense of agency for the Haru robot (see Fig. 1). To this end, we explore what kind of reactive responses humans find appropriate for a platform like Haru in different situations. Specifically, we conducted an elicitation study in which participants were asked to design Haru’s reactive response similar to either (1) that of a human, (2) a pet animal, or (3) in a freestyle manner befitting its design. Since Haru is neither clearly anthropomorphic nor zoomorphic, it is not straightforward what model would be most suitable to drive its behaviors. Our results show that, while participants design different types of behavior depending on their experimental group, it is possible to identify a range of behaviors used by all. This indicates that it is possible to design intuitively understandable reactive behaviors for a novel companion robot whose form has no clear analogue in nature. These behaviors are unique to Haru but contain elements from human and pet animal behaviors

Developing a robot's empathetic reactive response inspired by a bottom-up attention model

This paper describes the development of a reactive behavioral response framework for the tabletop robot Haru. The framework enables the robot to react to external stimuli through a repertoire of expressive routines. The behavioral response framework is inspired by the simple reactive behaviors of organisms (e.g. reflexes) based on a bottom-up attention model. First, a participatory study for behavior elicitation was conducted. We explored the possible expressive behaviors of the robot and the possible stimuli trigger. These stimuli-response (S-R) pairs are designed befitting the robot's characteristics. Then, we developed a perception and a reactive behavior module that automatically translates any perceived stimulus into expressive behavioral responses. We evaluated the proposed S-R framework using Haru in an interaction setting and our results show an increase in human attention activity indicative of its positive impact to conveying the robot's sense of agency