Takao Nakagawa

One of the difficult problems in the study of the constitutive equation for cyclic plasticity is the prediction of ratchetting behavior which is induced by the superposition of a cyclic secondary load to a constant primary load in the biaxial case, or by the mean stress in a uniaxial case. This paper shows the constitutive equation in which the memorization of the back stress was considered for ratchetting behavior, especially for biaxial ratchetting behavior. To verify the applicability of the constitutive equation to ratchetting behavior, biaxial ratchetting tests were carried out using type 304stainless steel at room temperature. As a result, it was found that the simulations based on the constitutive equation had good agreement with the tests.

An accurate attitude-control system of a mirror has been developped for a balloon-borne infrared interferometer. This system controls the mirror in arbitrary attitudes and achieves an accuracy of less than 0.2 arcsec. The drive mechanism and the attitude sensor were newly developped for this system. The components described in this paper, such as the actuator and the sensor as well as the overall controll system can be used in balloon environment.

The far-infrared [CII] line is a dominant coolant of neutral clouds and photodissociation regions. In order to make large scale survey observations of the [CII] line, we have built a new balloon-borne observing system called BICE (Balloon-borne Infrared Carbon Explorer). The BICE is a special system customized for the large-scale [CII] observations. Its telescope system consists of a off-set and over-sized optics. Its focal plane instrument is a Fabry-Perot spectrometer whose all optics are cooled with super-fluid liquid Helium. With these devices, the background radiation of the BICE system has been dramatically reduced, and thus the BICE has achieved an excellent sensitivity. We made two successful flights of the BICE in 1991 from Texas, U.S.A. The whole emissivity of the BICE system was measured to as low as 3.2%

Recent infrared observations of star-forming regions are reviewed. Low-mass stars are produced in dense cores of molecular clouds. Dense cores are not supported by supersonic turbulence, and have a free fall time of 10^5 years. Those stars with visual counterparts are more evolved objects, while those without visual conterparts are younger and have dust clouds around them. Near-infrared polarimetric observations and the energy distribution in the infrared show the existence disk structures around these pre-main-sequence stars.