A remarkable CER(colossal electroresistance) effect was observed in a series of polycrystalline Nd0.67Sr0.33MnO3 samples synthe-sized by high energy ball milling successive heat treatment.The CER ratio increased with ...A remarkable CER(colossal electroresistance) effect was observed in a series of polycrystalline Nd0.67Sr0.33MnO3 samples synthe-sized by high energy ball milling successive heat treatment.The CER ratio increased with increasing heating time and reached 3580% at a low temperature for the Nd0.67Sr0.33MnO3 ceramic annealed up to 13 h as measuring current was enhanced from 5 to 500 μA.The result showed that the CER effect was strongly dependent on the sample s microstructure,especially on the foreign phases whi...展开更多
Si 2N 2O ceramics was fabricated from powder by hot pressing in N 2 atmosphere. The resistance of the ceramic sample to oxidation and erosion of molten silica was investigated. The bulk density and open porosity of th...Si 2N 2O ceramics was fabricated from powder by hot pressing in N 2 atmosphere. The resistance of the ceramic sample to oxidation and erosion of molten silica was investigated. The bulk density and open porosity of the ceramic sample were measured according to the Archimedes principle in water. Then fracture surface of the sintered body was observed by SEM. The results and analysis indicate that the resistance of Si 2N 2O ceramics to oxidation and erosion of molten silica increases when its density increases and/or its open porosity decreases. Moreover, they also reveal that the oxidation process is an unsteady dispersing process with oxygen as the constant source, and the resistance to erosion of molten silica related to the quantity of grain boundary in unit surface area. The lowest mass gain is 2.4 g/m 2 after oxidizing at 1 000 ℃ for 100 h in air, while the lowest mass loss is 2.9 g/m 2 after 40 h erosion in molten silica.展开更多
Biomechanical properties of squid suckers were studied to provide inspiration for the development of sucker artefacts for a robotic octopus. Mechanical support of the rings found inside squid suckers was studied by be...Biomechanical properties of squid suckers were studied to provide inspiration for the development of sucker artefacts for a robotic octopus. Mechanical support of the rings found inside squid suckers was studied by bending tests. Tensile tests were carried out to study the maximum possible sucking force produced by squid suckers based on the strength of sucker stalks, normalized by the sucking areas. The squid suckers were also directly tested to obtain sucking forces by a special testing ar- rangement. Inspired by the squid suckers, three types of sucker artefacts were developed for the arm skin of an octopus inspired robot. The first sucker artefact made of knitted nylon sheet reinforced silicone rubber has the same shape as the squid suckers. Like real squid suckers, this type of artefact also has a stalk that is connected to the arm skin and a ring to give radial support. The second design is a straight cylindrical structure with uniform wall thickness made of silicone rubber. One end of the cylinder is directly connected to the arm skin and the other end is open. The final design of the sucker has a cylindrical base and a concave meniscus top. The meniscus was formed naturally using the surface tension of silicone gel, which leads to a higher level of the liquid around the edge of a container. The wall thickness decreases towards the tip of the sucker opening. Sucking forces of all three types of sucker artefacts were measured. Advantages and disadvantages of each sucker type were discussed. The final design of suckers has been implemented to the arm skin prototypes.展开更多
基金supported by the National Natural Science Foundation of China (10774040 and 10911120055/A0402)the Program for New Century Excellent Talents in University (NCET-08-0674)the Special Foundation for Young Scientists of Educational Commission of Hubei Province (Q200710008)
文摘A remarkable CER(colossal electroresistance) effect was observed in a series of polycrystalline Nd0.67Sr0.33MnO3 samples synthe-sized by high energy ball milling successive heat treatment.The CER ratio increased with increasing heating time and reached 3580% at a low temperature for the Nd0.67Sr0.33MnO3 ceramic annealed up to 13 h as measuring current was enhanced from 5 to 500 μA.The result showed that the CER effect was strongly dependent on the sample s microstructure,especially on the foreign phases whi...
文摘Si 2N 2O ceramics was fabricated from powder by hot pressing in N 2 atmosphere. The resistance of the ceramic sample to oxidation and erosion of molten silica was investigated. The bulk density and open porosity of the ceramic sample were measured according to the Archimedes principle in water. Then fracture surface of the sintered body was observed by SEM. The results and analysis indicate that the resistance of Si 2N 2O ceramics to oxidation and erosion of molten silica increases when its density increases and/or its open porosity decreases. Moreover, they also reveal that the oxidation process is an unsteady dispersing process with oxygen as the constant source, and the resistance to erosion of molten silica related to the quantity of grain boundary in unit surface area. The lowest mass gain is 2.4 g/m 2 after oxidizing at 1 000 ℃ for 100 h in air, while the lowest mass loss is 2.9 g/m 2 after 40 h erosion in molten silica.
文摘Biomechanical properties of squid suckers were studied to provide inspiration for the development of sucker artefacts for a robotic octopus. Mechanical support of the rings found inside squid suckers was studied by bending tests. Tensile tests were carried out to study the maximum possible sucking force produced by squid suckers based on the strength of sucker stalks, normalized by the sucking areas. The squid suckers were also directly tested to obtain sucking forces by a special testing ar- rangement. Inspired by the squid suckers, three types of sucker artefacts were developed for the arm skin of an octopus inspired robot. The first sucker artefact made of knitted nylon sheet reinforced silicone rubber has the same shape as the squid suckers. Like real squid suckers, this type of artefact also has a stalk that is connected to the arm skin and a ring to give radial support. The second design is a straight cylindrical structure with uniform wall thickness made of silicone rubber. One end of the cylinder is directly connected to the arm skin and the other end is open. The final design of the sucker has a cylindrical base and a concave meniscus top. The meniscus was formed naturally using the surface tension of silicone gel, which leads to a higher level of the liquid around the edge of a container. The wall thickness decreases towards the tip of the sucker opening. Sucking forces of all three types of sucker artefacts were measured. Advantages and disadvantages of each sucker type were discussed. The final design of suckers has been implemented to the arm skin prototypes.
