To what extent can we lower the critical temperature ratio (CTR) necessary to start a thermoacoustic engine? We present an experimental method for predicting the CTR before the temperature ratio arrives at it using quality factor measurements. Based on the experimental quality factors, we tried to decrease the CTR of a thermoacoustic Stirling engine consisting of a looped tube and a branch resonator. Installation of the multiple regenerators at suitable positions can markedly enhance acoustic power production while overcoming energy dissipation. Results show that the CTR is decreased from 1.76 to 1.19 using five differentially heated regenerators.
The optical properties of phosphate glass (PG) with two different impurities, namely, aluminum and tin, were investigated. Broad white luminescence was observed from PGs with tin and aluminum impurities under deep ultraviolet exposure. Through emission and excitation spectroscopy and decay curve measurement, it is assumed that the origin of the broadband luminescence differs depending on the impurities introduced. In addition, time-resolved emission spectral analysis revealed the difference in decay constant at each wavelength. The results obtained in this study might give important information about two potential impurities of PG for a better understanding of background noise and the functions of widely used radiophotoluminescence (RPL) dosimeters.
Sitting ability in the early post-stroke phase affects functional balance ability and other prognoses. We investigated whether dynamic sitting exercise with delayed visual feedback in the mediolateral and anteroposterior directions affected postural control in the early post-stroke phase. In this pilot randomized controlled trial, 27 hemiparetic stroke patients were randomized to experimental (n = 13) and control (n = 14) groups. Dynamic sitting exercise (30 times/day, 5 days/week) in the mediolateral and anteroposterior directions, with 500-ms-delayed (experimental group) or real-time (control group) visual feedback on a computer, was added to usual physical therapy. We evaluated the postural assessment scale for stroke (PASS), static and dynamic sitting balance tasks, the five-times sit-to-stand test, trunk impairment scale, functional ambulation category, and functional independence measure–motor items. In intention-to-treat analysis, the experimental group demonstrated a significant intervention effect on the PASS score (p < 0.05). The mean percentage of body weight on the moving side in the lateral sitting task and the number of successes in the five-times sit-to-stand test were significantly higher in the experimental group than those in the control group (P < 0.05). Thus, the proposed exercise improves postural control, dynamic sitting balance, and sit-to-stand ability in early post-stroke patients.
How much ean we lower the onset temperature ratio ( OTR )that is necessar } ' for a thermoacoustic engine to start? We tried te answer this question by installing a secondar ) ・ regenerator into a traveling wave englne consisting ofalooped tube and a branch resonator . Factors goveming the OTR were experimentally studied through measurcments of the quality factor at var 重 ous temperature ratios . It was found that the instailation of the secondary regenerator at a suitable position drastically enhamced themmoacoustic effects while introducing aslight damping to the system . As a resu 】 t, the OTR of the present thermoacoustic engine was decreased from 1. 76 to L 】 9, when the total number ofregenerators was increased to 5.
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