Thermal diffusivity measurement of 2.25Cr-1Mo steel with internal friction

In this work, the internal friction of 2.25Cr-1Mo steel measured on a dynamic mechanical analyzer (DMA) was used to evaluate its thermal diffusivity at elevated temperatures. With the dual cantilever clamp, the internal friction of 2.25Cr-1Mo steel at high temperatures was obtained, which was mainly composed of the thermoelastic relaxation with a peak of 15 Hz and the broad spectrum of relaxation processes especially at low frequencies. According to the deconvolution of these results, the thermoelastic internal friction of 2.25Cr-1Mo steel at high temperatures was achieved. Then, the thermal diffusivity of 2.25Cr-1Mo steel at high temperatures was quantitatively estimated, which confirmed the validity of present method.     

Analysis of precursors for crystal growth of YBaCuO thin films in magnetron sputtering deposition

We correlated the crystallinity of YBaCuO films prepared by magnetron sputtering deposition using Ar/O₂ mixture gas with the atomic and molecular composition in the gas phase. YBaCuO films were deposited on MgO substrates at 670 °C. Two-dimensional distributions of Y, Ba, Cu, YO, BaO, and CuO densities and one-dimensional distribution of O density were measured by laser-induced fluorescence spectroscopy. The Y and Ba densities decreased significantly with the increase of the O₂ partial pressure, and they were below the detection limit at an O₂ flow ratio of 10% and a total gas pressure of 53 Pa. The decrease in the Y and Ba densities was compensated by an increase in the YO and BaO densities. The decrease in the Cu density with the increase of the O₂ partial pressure was less significant, while the CuO density was below the detection limit at all the discharge conditions. The O density was evaluated to be 10¹²-10¹³ cm^− 3, which was much higher than the Cu density. On the other hand, YBaCuO films with high crystallinity were obtained at total gas pressures of 53-80 Pa and O₂ flow ratios of 50-70%. Therefore, it is concluded that the precursors for the deposition of YBaCuO films with high crystallinity are Cu, YO, BaO, and O.     

Attractive performance of a Gifford–McMahon cryocooler by co-axial layout of regenerator materials

A novel filling method of regenerator materials, which we name a co-axial layout, is experimentally investigated. The 2nd stage regenerator of a Gifford–McMahon cryocooler was packed with 50% by volume of the co-axial layout (low temperature side) that consisted of 20% Gd₂O₂S and 30% HoCu₂ spheres. The warm temperature side was packed with 50% lead spheres as a single layer. The experimental results show that the cooling power of co-axial layout is almost the same as that of a three-layer layout, 20% Gd₂O₂S, 30% HoCu₂ and 50% lead, at temperatures between the ultimate low temperature (3.0 K) and 6 K. Moreover, at the temperatures above 10 K, the co-axial layout has 1.7–2.0 times the cooling power of the three-layer layout. Thus the co-axial layout produces a major improvement in cooling power. In this paper, the performance of five types of material assortments is discussed.     

Sliding wear of YTZP ceramic against steel: observations on ceramic transfer and wear transition

Sliding tests were conducted, in air, of YTZP ceramic pins against steel discs at an applied pressure of 15.5 MPa over a speed range of 0.3 to 4.0 ms^–1. Pin wear was not detectable until 2.0 m s^–1, after which a finite but small wear rate was observed at 3.0 m s^–1, accompanied by a red glow at the contacting surface. A transition in wear behaviour and friction () occurred at 4.0 ms^–1, increasing the former by over two orders of magnitude. Both and wear behaviour changed with time at 4.0 m s^–1. During initial periods was high and wear rate increased steadily with time accompanied by ceramic transfer onto the disc, which increased with time. When disc coverage exceeds a certain threshold value, decreased rapidly and the wear rate stabilized at a very high value. Metal transfer was not observed at any speed. High surface temperatures brought about significant adhesion between TZP and steel and this together with enhanced plastic deformation brought about a transition in wear behaviour.     

Tongue-Movement Communication and Control Concept for Hands-Free Human–Machine Interfaces

A new communication and control concept using tongue movements is introduced to generate, detect, and classify signals that can be used in novel hands-free human-machine interface applications such as communicating with a computer and controlling devices. The signals that are caused by tongue movements are the changes in the airflow pressure that occur in the ear canal. The goal is to demonstrate that the ear pressure signals that are acquired using a microphone that is inserted into the ear canal, due to specific tongue movements, are distinct and that the signals can be detected and classified very accurately. The strategy that is developed for demonstrating the concept includes energy-based signal detection and segmentation to extract ear pressure signals due to tongue movements, signal normalization to decrease the trial-to-trial variations in the signals, and pairwise cross-correlation signal averaging to obtain accurate estimates from ensembles of pressure signals. A new decision fusion classification algorithm is formulated to assign the pressure signals to their respective tongue-movement classes. The complete strategy of signal detection and segmentation, estimation, and classification is tested on four tongue movements of eight subjects. Through extensive experiments, it is demonstrated that the ear pressure signals due to the tongue movements are distinct and that the four pressure signals can be classified with an accuracy of more than 97% averaged across the eight subjects using the decision fusion classification algorithm. Thus, it is concluded that, through the unique concept that is introduced in this paper, human-computer interfaces that use tongue movements can be designed for hands-free communication and control applications.     

Influence on the propulsive performance due to the difference in the fin shape of a robotic manta

This paper experimentally investigates the influence on the propulsive performance by the difference in the fin shape of a robotic manta. Five kinds of fin shapes, i.e., a rectangle, a triangle, a trapezoid, and two right triangles, are used in experiment to measure the forward speed of the robot, where two types of right triangle are discriminated, depending on the arrangement of the right angle part and each fin area is assumed to be approximately equal, and the number of fin rays is the same at all the fins. It is proved that a significant difference in propulsive speed arises depending on the difference in the fin shape. Some experiments are additionally conducted to examine the influence on the propulsive speed and its efficiency, due to the parameter change of a progressive wave in the fin.     

Frequency domain analyses of a thin liquid film surface by repetitively applied stress (dynamic response analyses by the long wave equation)

Numerical results were calculated for the dynamic behavior of an ultrathin liquid (lubricant) surface resulting from repetitively applied pressure and shear stress using the frequency domain equation and compared with those obtained using the time domain equation. Frequency domain analyses of the dynamic behavior of the ultrathin liquid (lubricant) surface produced by sinusoidally applied pressure and shear stress clarified the dependence of the liquid surface deformation on the frequency of the stresses and the disk speed. The dynamic behavior resulting from sinusoidally applied pressure and shear stress calculated using the time domain equation were found to gradually coincide with those obtained using the frequency domain equation.     

Effect of Speed and Pressure on Dry Sliding Interactions of Alumina against Steel

Sliding of alumina (87%) pins against a hardened steel disk over a range of pressures (3.3–30.0 MPa) and speeds (0.1–12.0 ms^-1) has been studied. Four different regions (R1, R2, R3, and R4) of friction as a function of speed have been identified. R1 and R3 exhibit single-valued friction while in R2 and R4 the friction exhibits dual behavior. The speed range over which these regions prevail is sensitive to the pressure. R1 and R2 are low-speed and low-temperature regions, and in both, metal transfer and formation and compaction of y-Fe₂O₃ occur. R3 and R4 are associated with high speeds and high interface temperatures. Formation of FeO, FeAl₂O₄, and FeAlO₃ has been observed. The implications of the tribochemical interactions on friction and wear characteristics are discussed.