Effects of solute and vacancy segregation on migration of a/4〈1 1 1〉 and a/2〈1 0 0〉 antiphase boundaries in Fe3Al

The effects of segregation of solute atoms and vacancies on migration of a/4〈1 1 1〉 and a/2〈1 0 0〉 antiphase domain boundaries (APDBs) in stoichiometric Fe₃Al at various temperatures are studied using a phase-field model [Koizumi Y, Allen SM, Minamino Y, Acta Mater 2008;56:5861] based on the Bragg–Williams approximation and kinetic parameters determined from experimental data. Boundary mobilities (M) were measured from the boundary velocity of shrinking circular antiphase domains (APDs). In the case of a/4〈1 1 1〉 APDBs, solute atmospheres follow the APDB until the APD vanishes by shrinking to zero radius, and therefore the Ms are always smaller than the intrinsic boundary mobilities because of the solute-drag effect. The M of a/4〈1 1 1〉 APDBs can be enhanced by up to 60% by vacancy segregation. On the other hand, the M of a/2〈1 0 0〉 APDBs is enhanced by only a few per cent. The a/2〈1 0 0〉 APDBs are observed to break away from the solute atmosphere during as the circular ABDBs shrink. The M increases by up to 40% associated with the breakaway, and becomes equal to the intrinsic boundary mobilities even though slight depletion and segregation of Al atoms remain ahead and behind the migrating boundary, respectively.     

Highly flame retardant coating consisting of starch and amorphous sodium polyborate

Mixture of starch and amorphous sodium polyborate (SPB) is found to show high flame retardancy, when its aqueous solution is deposited and dried on organic polymer materials such as polyethylene terephthalate (PET) nonwoven, rigid polyurethane (RPU) foam, and polypropylene (PP) nonwoven. The PET nonwoven (10 mm thickness) and the RPU foam (10 mm thickness) coated with the mixture endure the premixed flame of butane gas burner with length of 100 mm for more than 12 min. The PP nonwoven (0.7 mm thickness) endures the nonpremixed flame with length of 65 mm in the 45 degrees Meckel burner test for more than 2 min. The backside temperatures in the both tests remain below 130 °C. The thermal analyses and the SEM observation indicate the mechanism that the SPB foam promotes the carbonization of starch and that the carbonized layer together with the SPB foam insulate inside from oxygen and heat.     

Robotic question support system to reduce hesitation for face-to-face questions in lectures

Encouraging students to actively ask questions during lectures is a formidable challenge that can be addressed through innovative use of information technology. We developed a robotic system that allows students in a lecture to collaboratively decide questions to be asked by a humanoid robot. To verify whether the system reduces hesitation to ask questions during lectures, 62 university students were divided into two groups, and each attended two different mock lectures on the Nobel Prize in Physics. Two lectures were conducted with and without the proposed system in counterbalanced order. Results suggested that students who were usually hesitant to ask questions during lectures became less hesitant to ask questions face-to-face when they could use the proposed system. Moreover, the perceived activeness in the lectures increased when using the system. Multiple regression analyses revealed that certain student actions, particularly tweeting and showing agreement with the questions posted by others, were correlated with an increase in perceived activeness.     

A study of α- and β-phase poly(9,9-dioctylfluorene) by electroabsorption spectroscopy

The excited-state structure of β-phase poly(9,9-dioctylfluorene) (F8) is investigated by means of optical absorption and electroabsorption spectroscopies in order to reveal the effect of β-phase formation on the excited-state structure in F8. The excited-state structure of β-phase F8 consists of six essential states, where two new B_u states are formed on the four essential states of α-phase F8. The two additional B_u states result from the energy splitting of the B_u states of α-phase F8, caused by intermolecular interaction in β-phase F8.     

Digital tracking control of space robots using a transpose of the generalized Jacobian matrix

We have proposed discrete time-control methods using the transpose of the generalized Jacobian matrix (GJM) for free-floating space robots having manipulators. The control methods are robust for singular configurations of robots. Since the methods belong to a class of constant-value control, in this article we propose a digital trajectory tracking control method using the transpose of the GJM. Computer simulations show the effectiveness of the proposed method. This work was presented in part at the 11th International Symposium on Artificial Life and Robotics, Oita, Japan, January 23–25, 2006