Shape error measurement using ray-tracing and fringe scanning methods: projection of grating displayed on a liquid crystal panel

We present an improved Hartmann test, which has high spatial resolution with respect to the measuring points, for measuring projection mirrors. In the method, grid lines with a sinusoidal transmittance distribution are displayed on a liquid crystal panel and illuminated with a collimated laser beam. The beam transmitted through the liquid crystal panel reflects off the mirror surface being tested and reaches a screen. A charge-coupled device camera detects the projected images, which contain information about the inclination of the surface being tested. Any error in the shape of the mirror surface is identified by integrating the inclination. To increase the spatial resolution, the fringe scanning method is performed by shifting the grid lines on the liquid crystal panel. The grid lines are optimized for the shape of the mirror being tested. Because the grid lines are displayed by an electrical method, the shifting operation is easy and rapid, and furthermore, the displacement can be done precisely. The shape error of an off-axis parabolic mirror made of plastic is measured by the proposed method.     

Wide gap p-type degenerate semiconductor: Mg-doped LaCuOSe

Hole transport and optical properties were investigated on undoped and Mg-doped LaCuOS_1−xSe_x (x=0-1) epitaxial films. Both electrical conductivity and Hall mobility were found to increase monotonously with increasing Se content in the films. The increase in Hall mobility is considered to be associated with the increase in valence band dispersion. Mg ion doping increased hole concentrations in the undoped films by an order of magnitude to ∼2×10²⁰ cm⁻³, while Mg doping reduced mobility to merely half that of undoped films. The results suggest that hole scattering due to Mg impurity ions is suppressed by natural modulation doping originating from the layered structure of LaCuOS_1−xSe_x. Hole concentrations showed no temperature dependence, indicating degenerate conduction. The largest value for conductivity, 140 S cm⁻¹, was obtained with Mg-doped LaCuOSe epitaxial film. Accompanying characteristics included moderately high optical transparency in the visible region and blue photoluminescence.     

Study on effects of negative driving torque in servomotor drivers

Many applications, such as elevators, electric cars and robotic applications, require a servomotor driver capable of controlling a motor to drive its load with either positive or negative driving torque. The negative driving torque is defined as torque applied to a load in the reverse direction of motor rotation. In a servomotor driver with a switching amplifier, when the motor drives its load with negative driving torque, effects of negative driving torque might damage the servomotor driver and complicate dynamic characteristics of the servomotor system. Thus, in order to investigate effects of the negative driving torque in servomotor drivers, this paper uses the numerical simulation that combines the simulation of a control system with that of electronic circuits. The simulation results show that the negative driving torque is required for decelerating and compensating disturbance. During decelerating and compensating disturbance, the pulse-width modulation (PWM) amplifier of a servomotor driver will generate regenerative current that flows from the motor back into the power supply, and then makes the power supply voltage rise.     

Zone-plate inteferometer to measure the positioning error of a cutting tool

A simple type of zone-plate interferometer has been developed to measure precisely the positioning error of a cutting tool. Interference fringes obtained by the interferometer are little affected by air turbulence in the optical paths and by machine vibrations. The shape of the mirrors surface being tested is spherical and is manufactured with an ultraprecision lathe. A zone plate is set at the midposition between the vertex of the spherical mirror being tested and the center of curvature of the mirror. The error in the shape of the mirror and the positioning error of the tool can be determined by analyzing the interference fringes. Two spherical concave mirrors were measured. One mirror was manufactured with a tool that had same positioning error. The positioning error was observed as distortion of the interference fringes. The images obtained by the zone-plane interferometer agree well with the images obtained by a Fizeau interferometer and a computer simulation based on the experimental results. The other mirror was manufactured with the tool after the positioning error had been eliminated, based upon the results of the above experiments. The interference fringes of the mirror show no distortion, and the error in the shape of the mirror is small.     

A novel evaluation method for interfacial adhesion strength in ductile dissimilar materials

The energy of interface adhesion between two elastic–plastic materials was directly evaluated as the mechanical work supplied exclusively to separate the interface. Interface crack extension was simulated by elastic plastic finite element models, where the nodes along the interface in the vicinity of crack tip were divided into two nodes and the nodal forces were gradually decreased to zero. While further plastic deformation takes place in the volume of materials during crack extension, the work done by these nodal forces against mutual displacement of crack surfaces should be consumed on the surfaces and thus equals to the interface adhesion energy. This technique was applied to a copper/polyimide system for flexible printed circuits in accordance with the new experimental results. In comparison to the results obtained by the conventional peel test, this technique yielded far smaller amount of interface energy successfully excluding the energy dissipated with bulk plastic deformation without any insertion of cohesive strip along the interface in the model.     

High-throughput screening of improved protease inhibitors using a yeast cell surface display system and a yeast cell chip

Protease-targeted inhibitors have been promising pharmaceuticals. Here, we combined a yeast cell surface display system with a yeast cell chip for the high-throughput screening of protease inhibitors, and succeeded in improving the activity of a protease inhibitor.     

Temperature-swing adsorption of proteins in water using N-isopropylacrylamide copolymer gel particles

The adsorption and desorption behaviors of bovine serum albumin (BSA) in water for temperature-responsive polymer gel particles have been investigated by the temperature-swing operation between 298 and 313 K, where the cationic N-isopropylacrylamide (NIPA) gels copolymerized with vinylbenzyl trimethylammonium chloride (VBTA) or 2-(dimethylamino)ethyl methacrylate (DMAEMA) were used. The NIPA-VBTA and the NIPA-DMAEMA copolymer gels adsorbed BSA while the NIPA homopolymer gel hardly adsorbed BSA, indicating that the copolymer gels adsorb BSA through the electrostatic attraction between the positively charged groups in the gels and the negatively charged BSA. The adsorption amounts for the NIPA-DMAEMA gels were smaller than those for the NIPA-VBTA gels. This may be because almost every VBTA group, which is a quaternary ammonium salt, can be positively charged in water, while only some of the tertiary amine DMAEMA groups are protonated in water. Moreover, it was found that both the copolymer gels with a large mesh size of the polymer network repeatedly adsorbed BSA at 298 K and desorbed some of pre-adsorbed BSA at 313 K by the temperature-swing operation. This BSA desorption may result from the decrease of the number of the positively charged groups accessible to BSA due to the shrinking of the constituent polymer chains.