This manuscript summarizes studies on earthquake source physics by the author, with some explanations of the influence of very large earthquakes in this study field. The author has been working on the whole generation process of earthquakes, from tiny rock failure to mega-earthquakes, mainly using seismic data analysis, also based on elasto-mechanics, fracture criterions, and friction laws. These studies confirmed that earthquakes are characterized by wide scale range, without limitation of specific sizes. There is little difference in the initial processes of dynamic rupture of micro and mega earthquakes. Numerical models for such wide-scale phenomena may require some hierarchal structures, which are also essential to make any prediction and forecast for future earthquakes. The knowledge for earthquake generation must be also utilized to understand other phenomena governed by power laws.
This paper reports the investigation of tactile mechanism and a development of a tactile sensor system Details of the sense of roughness and hardness are investigated through several sensory tests and measurement experiments. The tactile motion / operation of skilled and amateur are measured and the measurement data are compared to extract the difference. The tactile sensor system based with the characteristics of human finger motion and skin sensory receptors is succeeded in measuring human touch feelings.
Self-assembled monolayer (SAM) with amphiphilic linear molecules has been studied as a surface modifier. In general, the surface properties of a SAM are dependent on the chain end chemistry of the molecules. Thus, a SAM composed of alkane loops from cyclic alkanedisulfide on a gold substrate, in which both sulfurs are bound to gold, may possess unique surface properties due to the chain folding as well as a lack of chain ends. We here focus on the frictional properties of the linear and cyclic SAMs. For the cyclic SAM, the load dependence of the frictional force became more striking beyond a threshold. Such a frictional transition was not observed for the corresponding linear SAM. The load-induced transition in the frictional response from the alkane loops could be related to the conformational change of the alkane loops, which collapsed along the direction normal to the SAM surface.
Tribotronics is a word made from Tribology and Electronics, it refers to the idea of controlling the tribological system by outputs of electron emission, tribological static-charge, the frictional heat, and wear etc. In this explanation, applications in head-disk interface, tribological power generation, sensors using triboelectric charging, applications in control of friction and wear are discussed.
About Okayamaʼs cultural properties, this article describes the technology related to industry and tribology. Iron-making industry thrived in the ancient Kibi area. As a result, utilization of iron oxide can be seen in various cultural properties. Iron oxides were used as red iron oxide for abrasives and red colorants. Furthermore, red color development with iron oxide can be seen even in Bizen pottery. Other interesting facilities such as bearings that smoothly rotate huge stone windmills are also described.
We investigated properties of lubricants confined between mica surfaces using resonance shear measurement (RSM) which can monitor the rheological and tribological properties of the lubricants as a function of the surface separation distance (D) as well as the normal load (L). The formulations of the five lubricants investigated were; oil A (mineral oil + viscosity modifier (VM) + Antiwear additive + Metallic detergent + Ashless dispersant + Anti-oxidant + Foam inhibitor), oil B (oil A + Molybdenum dithiocarbamate (MoDTC)), oil-C (oil A + Glycerol monooleate (GMO)), oil D (mineral oil + viscosity modifier (VM)), and oil E (mineral oil only). The oil E showed the friction coefficient (µ) of 0.45 at the normal load (L) below 2.0 mN. The oil D, which contained VM, showed significant decrease in the µ value to 0.19. In the case of oil A, B, C, the thickness of lubricant layers became significantly thicker than those of oil E and D, however, the no clear reduction in the µ value compared with oil D was observed. These results have demonstrated that the RSM can evaluate the contribution of the each component on the lubrication in order to optimize their properties and performance.
Thermo-hydrodynamic lubrication (THL) models have been applied at the design stage of large-sized high-speed rotary machineries to confirm that the maximum surface temperature of sliding bearing, such as tilting pad journal bearing, under operation is below the upper limit. A single common value of heat transfer coefficient is given between the environment and the five surfaces other than the lubricating one of each pad regardless of operating conditions and/or bearing specifications in the traditional THL model, while a new THL model is proposed with non-traditional heat transfer model incorporated. In this model, the value of locally distributed heat transfer coefficient is determined depending on the operation conditions and/or the bearing specifications. Using the model, it is unnecessary to determine the heat transfer coefficient by an unreasonable estimation, and it is found that the predicted maximum pad surface temperature and also the distribution of pad surface temperature are in good agreement with the measurements.