Some properties of four-dimensional multicounter automata

Recently, due to the advances in many application areas such as computer animation, motion image processing, and so forth, it has become increasingly apparent that the study of four-dimensional pattern processing is of crucial importance. Thus, we think that research into four-dimensional automata as a computational model of four-dimensional pattern processing is also meaningful. This article introduces four-dimensional multicounter automata, and investigates some of their properties. We show the differences between the accepting powers of seven-way and eight-way four-dimensional multicounter automata, and between the accepting powers of deterministic and nondeterministic seven-way four-dimensional multicounter automata. This work was presented in part at the 10th International Symposium on Artificial Life and Robotics, Oita, Japan, February 4–6, 2005     

High‐efficiency UV LEDs using quaternary InAlGaN

High‐efficiency ultraviolet (UV) light sources are very attractive for application to the medical field, white lighting, high‐density memories, and so on. We have demonstrated that 300‐ to 370‐nm UV emission is considerably enhanced by the introduction of several percent of In into AlGaN due to an In‐segregation effect. We fabricated 310‐nm‐band UV LEDs with quaternary InAlGaN emitting layers on a sapphire substrate and obtained submilliwatt output power. We also fabricated 350‐nm‐band InAlGaN‐based quantum‐well LEDs on GaN substrates in order to eliminate the effects of threading dislocations. The maximum UV output power obtained was as high as 7.4 mW under room‐temperature CW operation. The maximum external quantum efficiency (EQE) was 1.1% with an injection current of 50 mA, which is the highest EQE ever obtained for 350‐nm‐band UV LEDs with top‐emission geometry. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(3): 43–51, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20287 Copyright © 2006 Wiley Periodicals, Inc.     

Dust particle formation due to interaction between graphite and helicon deuterium plasmas

The collection of dust particles using divertor simulation helicon plasmas has been carried out to examine dust formation due to the interaction between a graphite target and deuterium plasmas, which are planned to operate in the large helical device (LHD) at the Japanese National Institute for Fusion Science (NIFS). The collected dust particles are classified into three types: (i) small spherical particles below 400 nm in size, (ii) agglomerates whose primary particles have a size of about 10 nm, and (iii) large flakes above 1 μm in size. These features are quite similar to those obtained through hydrogen plasma operation, indicating that the dust formation mechanisms due to the interaction between a carbon wall and a plasma of deuterium, which is the isotope of hydrogen, is probably similar to those of hydrogen.     

Anisotropic elastic constants and thermal expansivities in monocrystal CrB2, TiB2, and ZrB2

The elastic constants and thermal expansivities in monocrystals of three transition-metal diborides with the AlB₂ structure, CrB₂, TiB₂, and ZrB₂, have been investigated in the temperature ranges from 300 to 1373 K and from 300 to 1073 K. The anisotropic parameters deduced from the measured elastic constants and thermal expansivities indicate that of the three diborides, the anisotropy is the most and least significant in CrB₂ and ZrB₂, respectively. The factors determining the significance in anisotropy in atomic bonding in AlB₂-type diborides are analyzed by an approach similar to the valence-force-field method and are discussed in terms of the deformation of the electronic charge around the metal atoms occurring to fit themselves in the (0 0 0 1) basal plane.     

Evolution of orientation distributions of γ and γ′ phases during creep deformation of Ni-base single crystal superalloys

The evolution of orientation distributions of γ and γ′ phases in crept Ni-base single crystal superalloys have been investigated by theoretical calculations with elastic–plastic models and by experiments. As creep deformation proceeds, the crystallographic orientation distributions for both phases are broadened as a result of the waving of the raft structure, which occurs to reduce the total mechanical energy. The broadening of the orientation distribution occurs in such a way that the 0 0 1 pole broadens isotropically while the h k 0 poles broaden preferentially along the 〈0 0 1〉 directions. Since the extent of the broadening increases almost linearly with the number of creep deformation, the measurement of the broadening by X-ray diffraction can be utilized in non-destructive methods to predict the lifetime of Ni-base superalloys.     

A parallel link end effector for scanning electrical discharge machining process

Because a parallel mechanism has a high-frequency response, multiple degrees of freedom (DOF), and high stiffness, it can be applied to an end effector for electrical discharge machining (EDM) with a scanning motion. A prototype has 3 DOF: two tilting angles around the x- and y-axes, and the movement in the z-direction. It consists of, a base plate, a stage, a constraint link, and three inchworm devices that act as links. The inchworm devices are connected with the stage and the base plate. The z-position and inclination of the stage are changed by adjusting the length of the inchworm devices. The electrode feeding is controlled by the combination of the steplike movement with the inchworm devices and continuous extension of piezos. The frequency response of the stage by the continuous extension of the piezos is up to 200 Hz. The positioning accuracy of the end effector is less than 30 μm in height and 0.04° in inclination. Some examples of EDM by the scanning motion are demonstrated.     

Shape difference visualization for ancient bronze mirrors through 3D range images

Japanese archaeologists have paid special attention to ancient Chinese bronze mirrors because the mirrors may provide a key for the exact location of Yamatai State, which is one of the major archaeological controversies. Currently, archaeologists visually analyse ancient Chinese bronze mirrors for their shape difference. The practice requires a huge amount of time and effort. In this paper, we propose an automatic method for detecting the shape difference between a pair of ancient mirrors. The 3D data of the mirrors are obtained using a laser range scanner. Our algorithm then aligns them into the same coordinate and visualizes their shape differences. Our proposed algorithm provides fast and non‐damaging analysis for shape difference. Further analysis can be evaluated on our data instead of the actual mirror, so it can be performed by more than one group of archaeologists. Copyright © 2003 John Wiley & Sons, Ltd.     

Multiple degrees-of-freedom arm with passive joints for on-the-machine measurement system by calibrating with geometric solids

To fabricate three-dimensional profiles with high accuracy, on-the-machine measurement is useful. Methods for the on-the-machine measurement by calibration with geometric solids used for references have been developed. In this paper, an arm with passive joints for on-the-machine measurement is proposed. As a prototype, the arm has 4 degrees of freedom (DOF) including two passive joints. The probing system has 7 DOF, including the DOF of the machine tool, in total. Angles of the passive joints are changed by driving the numerically controlled (NC) table and the main spindle of the machine tool, where the arm is mounted. To calculate the optimal posture of the arm for the shape to be measured, a numerical method of the inverse kinematics is also proposed. The arm has enough positioning accuracy to calibrate its posture. Shapes can be automatically measured with the accuracy of micrometer order by the on-the-machine measurement method as well as a commercial three-dimensional (3-D) coordinate measuring machine and a profilometer.