Measurements of Antenna Surface for Millimeter-Wave Space Radio Telescope

In the construction of a space radio telescope, it is essential to use materials with a low noise factor and high mechanical robustness for the antenna surface. We present the results of measurements of the reflection performance of two candidates for antenna surface materials for use in a radio telescope installed in a new millimeter-wave astronomical satellite, ASTRO-G. To estimate the amount of degradation caused by fluctuations in the thermal environment in the projected orbit of the satellite, a thermal cycle test was carried out for two candidates, namely, copper foil carbon fiber reinforced plastic (CFRP) and aluminum-coated CFRP. At certain points during the thermal cycle test, the reflection loss of the surfaces was measured precisely by using a radiometer in the 41-45 GHz band. In both candidates, cracks appeared on the surface after the thermal cycle test, where the number density of the cracks increased as the thermal cycle progressed. The reflection loss also increased in proportion to the number density of the cracks. Nevertheless, the loss of the copper foil surface met the requirements of ASTRO-G at the end of the equivalent life, whereas that of the aluminum-coated surface exceeded the maximal value in the requirement even before the end of the cycle.Comment: 11 pages, 6 figures, accepted for publication in PAS

Simulation assisted study on structural degradation in advanced SiC/SiC CMC component during high-temperature fatigue

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Influence of Setting Condition on Characteristics of Savonius Hydraulic Turbine with a Shield Plate

The aim of this investigation was to improve power performance of Savonius hydraulic turbine utilizing small stream for electric generation. An attempt was made to increase the power coefficient of runner by the use of flat shield plate placed upstream of the runner. The difference of the power coefficient is discussed in relation to clearance between the runner and the bottom wall and the rotation direction of the runner. The flow field around the runner was also examined visually to clarify influences of setting conditions on the power performance. From this study it was found that the power coefficient is achieved for 0.47 by only using a flat shield plate, the increase is up to 80% over the runner without the plate. Moreover, it is the proper condition that clearance ratio is 0.73 in this study.ArticleJOURNAL OF THERMAL SCIENCE. 20(3):224-228 (2011)journal articl

Footballer's Lateral Meniscus: Anterior Horn Tears of the Lateral Meniscus with a Stable Knee

This paper aimed to identify the characteristics of isolated anterior horn tear of the lateral meniscus in footballers who underwent arthroscopic surgery. We identified 8 patients with stable knee and no ligament injury, who had only isolated anterior horn tear of the lateral meniscus between 2007 and 2009. All 8 patients were footballers, comprising 7 men and 1 woman with mean age of 18.6 years. Arthroscopy revealed multiple longitudinal tears in 2 patients, longitudinal tear in 2 patients, degenerative tear in 3 patients, and flap tear in 1 patient. Two patients were treated by repair, five by partial excision, and one by rasping only. The mean Lysholm score was 65 before surgery and recovered to 89 at the last followup, on average 12 months after surgery. Anterior horn tear of the lateral meniscus in footballers with a stable knee is characterized by pain at the anterolateral aspect of the knee during knee extension, especially when kicking a ball, and pain during weight-bearing knee extension, together with MRI finding of hyperintense signal in the anterior horn of the lateral meniscus. Preoperative diagnosis may be possible based on these findings in footballers

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Report: The Relative Merits of the Modified Sag-Tape Method for Determining Instream Flow Requirement