Nature © Macmillan Publishers Ltd 1997the same direction. A zero value of H j indicates ferromagnetically coupled films. H j is known 7,14 to oscillate as a function of t because of the RKKY interaction. We can clearly distinguish two situations. In Fig. 4b (Cu spacer grown at room temperature) only a few oscillations take place, the oscillation with the short wavelength l being marginal. This is in contrast to the theoretical expectations 7 , which require l to dominate over Λ for geometrically perfect samples. On the other hand, when the Cu spacer is grown at low temperatures, more oscillations appear (Fig. 4c), and l dominates over Λ. We note that cooling a room-temperature-deposited wedge structure does not change the results given in Fig. 4b. Thus, lowtemperature deposition is essential to minimize thickness fluctuations. We also note that, in for example Fe/Cr multilayers, just the opposite occurs: the shortest-wavelength oscillation is favoured by high-temperature growth 15 .The smallest oscillations detected in this experiment correspond to an energy change of ϳ10 −8 eV per atom. This value represents a challenge both to first-principles calculations and to spectroscopies aimed at unveiling the electronic structure of solids. Moreover, although exceedingly small, this energy scale participates in deter-mining a macroscopic observable (in this case the threshold magnetic field H s ) and thus might play an important role in the design of metallic nanostructures for device application. Ⅺ

Abstract-Intelligent vehicle cooperation based on reliable communication systems contributes not only to reducing traffic accidents, but also to improving traffic flow. Adaptive Cruise Control (ACC) systems can gain enhanced performance by adding vehicle-vehicle wireless communication to provide additional information to augment range sensor data, leading to Cooperative ACC (CACC). This paper presents the design, development, implementation and testing of a CACC system. It consists of two controllers, one to manage the approaching maneuver to the leading vehicle and the other to regulate car-following once the vehicle joins the platoon. The system has been implemented on four production Infiniti M56s vehicles, and this paper details the results of experiments to validate the performance of the controller and its improvements with respect to the commercially available ACC system.

Inorganic solids with wide bandgaps are usually classified as electrical insulators and are used in industry as insulators, dielectrics, and optical materials. Many metallic oxides have wide bandgaps because of the significant contribution of ionic character to the chemical bonds between metallic cations and oxide ions. Their ionic nature simultaneously suppresses the formation of easily ionizable shallow donors or acceptors and enhances the localization of electrons and positive holes. Thus it is understandable that interest in these wide-gap oxides as conductive materials has not been strong.

β- Ga 2 O 3 single crystals were grown by the floating zone method and their conductivity along the b axis was controlled from <10−9 to 38 Ω−1 cm−1 by changing the growth atmosphere. By using feed rods doped with Sn, the grown crystal became highly conductive even under oxidative atmosphere. The optical transmission spectra showed that the β-Ga2O3 single crystal with 0.32 mm was transparent in the visible and ultraviolet region, with 20% transmittance at the fourth-harmonic wave of the Nd:YAG laser (266 nm). The band-gap widening was observed with the increasing of the carrier concentration. It is expected that the light of the KrF laser can be transmitted in the heavily doped β-Ga2O3.

Transparent p-type conducting CuGaO2 thin films were prepared on α-Al2O3 (001) single-crystal substrates by pulsed laser deposition. The films were grown epitaxially on the substrates in an as-deposited state. X-ray pole figure analysis revealed that the films were composed of two types of epitaxial grains, both with c axes oriented perpendicular to the surface and a axes rotated 60° with respect to each other around the c axis. Observation of the CuGaO2 thin films by atomic force microscopy and high-resolution transmission electron microscopy substantiated this conclusion. The films have high optical transparency (∼80%) in the visible region, and the energy gap of CuGaO2 for direct allowed transition was estimated to be 3.6 eV. p-type conductivity was confirmed by Seebeck and Hall measurements. The electrical conductivity, carrier (positive hole) density, and Hall mobility of the films at room temperature were 6.3×10−2 S cm−1, 1.7×1018 cm−3, and 0.23 cm2 V−1 s−1, respectively.